Semiconductor device having radiation structure

ABSTRACT

A semiconductor device includes two semiconductor chips that are interposed between a pair of radiation members, and thermally and electrically connected to the radiation members. One of the radiation members has two protruding portions and front ends of the protruding portions are connected to principal electrodes of the semiconductor chips. The radiation members are made of a metallic material containing Cu or Al as a main component. The semiconductor chips and the radiation members are sealed with resin with externally exposed radiation surfaces.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of JapanesePatent Applications No. 11-333119 filed on Nov. 24, 1999, No. 11-333124filed on Nov. 24, 1999, No. 2000-88579 filed on Mar. 24, 2000, No.2000-97911 filed on Mar. 30, 2000, No. 2000-97912 filed on Mar. 30, 2000and No. 2000-305228 filed on Oct. 4, 2000, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a semiconductor device in which heat isradiated from both sides of a semiconductor chip accommodated therein.

[0004] 2. Description of the Related Art

[0005] For example, JP-A-6-291223 discloses a semiconductor device inwhich heat is radiated from both sides of a semiconductor chip. FIGS. 1Ato 1C show this semiconductor device. As shown in the figures, a pair ofradiation members J2, J3 sandwich several semiconductor chips J1, andare thermally and electrically connected to the semiconductor chips J1.The several semiconductor chips J1 arranged on a plane and the radiationmembers J2, J3 are sealed with resin J5.

[0006] Each of the radiation members J2, J3 serves as an electrode, andhas a surface exposed from the resin J5 at an opposite side of the facecontacting the semiconductor chips J1. Each of the radiation members J2,J3 performs radiation of heat by making the exposed surface contact acontact body (not shown) that can exhibit a radiation action. A controlterminal J4 connected with a control electrode of the semiconductorchips J1 protrudes to an outside from the resin J5.

[0007] Used as the radiation members J2, J3 is W (tungsten) or Mo(molybdenum) having a thermal expansion coefficient approximate to thatof the semiconductor chips J1. The radiation member J2 that is connectedto the surfaces of the semiconductor chips J1 on which the controlelectrode is formed is an emitter electrode, and the radiation member J3that is connected to the surfaces of the semiconductor chips J1 at anopposite side of the control electrode is a collector electrode.

[0008] Besides, several solder bumps J7 protrudes from an insulatingplate J6 that has a through hole at a center thereof in which theradiation member J2 penetrates as the emitter electrode. The solderbumps J7 are bonded to bonding pads existing in unit patterns of therespective semiconductor chips J1 disposed on the radiation member J3 asthe collector electrode.

[0009] When the radiation members J2, J3 serving also as electrodes aremade of metallic material such as W or Mo having linear thermalexpansion coefficient approximate to that of the semiconductor chips J1made of Si (silicon), these metallic materials are, in electricalconductivity about one third of that of Cu (copper) or Al (aluminum),and in thermal conductivity about one third to two third thereof. Thus,in the present circumstances involving an increased requirement forflowing a large current in the semiconductor chip, using W or Mo as amember that serves as a radiation member and an electrode simultaneouslycauses many problems.

[0010] Also, in general, a larger chip is required to accommodate alarger current. However, there are many technological problems toincrease the chip size, and it is easier to manufacture plural smallerchips and accommodate them into one package.

[0011] In the technique disclosed in the publication describe above, theseveral semiconductor chips J1 are formed in the semiconductor device.However, as shown in FIG. 1A, because the radiation member J2 has asimple rectangular shape, and is provided at the center of the device,disposal of different semiconductor chips in one device is limited. Thatis, when the semiconductor chips are different from one another in, forexample, thickness, it is difficult for the one emitter electrode havinga simple shape to be connected to all of the different semiconductorchips.

SUMMARY OF THE INVENTION

[0012] The present invention has been made in view of the above problem.An object of the present invention is to improve a radiation propertyand an electrical conductivity of a semiconductor device includingradiation members that are thermally and electrically connected to bothsurfaces of a semiconductor chip therein. Another object of the presentinvention is to provide a semiconductor device easily accommodatingseveral different semiconductor chips therein.

[0013] For example, according to one aspect of the present invention, ina semiconductor device in which a semiconductor chip is thermally andelectrically connected to first and second radiation memberstherebetween, the first and second radiation members are made of ametallic material that is superior to tungsten and molybdenum in atleast one of an electrical conductivity and a thermal conductivity.Accordingly, the radiation property and the electrical conductivity ofthe semiconductor device can be improved.

[0014] According to another aspect of the present invention, in asemiconductor device in which first and second semiconductor chips arethermally and electrically connected to first and second radiationmembers therebetween, the first radiation member has first and secondprotruding portions protruding toward the first and second semiconductorchips, and first and second front end portions of the first and secondprotruding portions are thermally and electrically connected to thefirst and second semiconductor chips through a bonding member.

[0015] In this case, even when the first and second semiconductor chipsare different from each other in thickness, the first and secondradiation members can be provided with first and second radiationsurfaces approximately parallel to each other by controlling protrudingamounts of the first and second protruding portions.

[0016] According to still another aspect of the present invention, in asemiconductor device in which a semiconductor chip is disposed between,a first conductive member and a second conductive member, the firstconductive member is further bonded to a third conductive member at anopposite side of the semiconductor chip so that a bonding area betweenthe first conductive member and the third conductive member is smallerthan that between the first conductive member and the semiconductorchip. Accordingly, stress concentration on the first conductive membercan be suppressed to prevent occurrence of cracks. This results inimproved radiation property and electrical conductivity of thesemiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other objects and features of the present invention will becomemore readily apparent from a better understanding of the preferredembodiments described below with reference to the following drawings, inwhich;

[0018]FIG. 1A is a schematic view showing a semiconductor deviceaccording to a prior art;

[0019]FIG. 1B is a cross-sectional view showing the semiconductordevice, taken along line IB-IB in FIG. 1A;

[0020]FIG. 1C is a cross-sectional view showing the semiconductordevice, taken along line IC-IC in FIG. 1A;

[0021]FIG. 2A is a cross-sectional view showing a semiconductor devicein a first preferred embodiment;

[0022]FIG. 2B is an enlarged cross-sectional view showing a partindicated by arrow IIB in FIG. 2A;

[0023]FIG. 3 is a table showing metals usable for a radiation member inthe first embodiment;

[0024]FIG. 4A is a cross-sectional view partially showing asemiconductor device in a second preferred embodiment;

[0025]FIGS. 4B to 4D are cross-sectional views respectively showing afirst side radiation member and a Si chip in the second embodiment;

[0026]FIGS. 5A to 5C are cross-sectional views respectively taken alonglines VA-VA, VB-VB, and VC-VC in FIGS. 4B to 4D;

[0027]FIG. 6 is a cross-sectional view showing a semiconductor device ina third preferred embodiment;

[0028]FIG. 7 is a cross-sectional view showing a semiconductor device ina fourth preferred embodiment;

[0029]FIG. 8A is a cross-sectional view showing a semiconductor devicein a fifth preferred embodiment;

[0030]FIG. 8B is a cross-sectional view taken along line VIIIB-VIIIB inFIG. 8A;

[0031]FIG. 9A is a cross-sectional view showing a semiconductor devicein a sixth preferred embodiment;

[0032]FIG. 9B is an enlarged cross-sectional view showing a partindicated by arrow IXB in FIG. 9A;

[0033]FIG. 9C is a cross-sectional view showing an example in the sixthembodiment;

[0034]FIG. 10 is a cross-sectional view showing a semiconductor devicein a seventh preferred embodiment;

[0035]FIG. 11 is a cross-sectional view showing a semiconductor devicein an eighth preferred embodiment;

[0036]FIG. 12 is a cross-sectional view showing a semiconductor devicein a ninth preferred embodiment;

[0037]FIG. 13 is a cross-sectional view showing a semiconductor devicein a tenth preferred embodiment;

[0038]FIGS. 14A to 14C are cross-sectional views showing a method formanufacturing the semiconductor device shown in FIG. 13 in a stepwisemanner;

[0039]FIG. 15 is a cross-sectional view schematically showing a secondlead member and a soldering member as a modified example of the tenthembodiment;

[0040]FIG. 16 is a cross-sectional view schematically showing a methodfor manufacturing a semiconductor device in an eleventh preferredembodiment;

[0041]FIG. 17 is a cross-sectional view schematically showing a methodfor manufacturing a semiconductor device in a twelfth preferredembodiment;

[0042]FIG. 18 is a cross-sectional view schematically showing anothermethod for manufacturing the semiconductor device in the twelfthembodiment;

[0043]FIG. 19 is a cross-sectional view showing a semiconductor devicein a thirteenth preferred embodiment;

[0044]FIGS. 20A to 20C are cross-sectional views for explaining a methodfor manufacturing the semiconductor device shown in FIG. 19;

[0045]FIG. 21 is a cross-sectional view showing a semiconductor devicein a fourteenth preferred embodiment;

[0046]FIG. 22 is a cross-sectional view showing a semiconductor devicein a fifteenth preferred embodiment;

[0047]FIG. 23 is a cross-sectional view showing a semiconductor deviceas a modification of the thirteenth embodiment;

[0048]FIG. 24 is a cross-sectional view showing a semiconductor devicein a sixteenth preferred embodiment;

[0049]FIG. 25 is an enlarged cross-sectional view showing a partsurrounded by a broken line in FIG. 24;

[0050]FIG. 26 is a top plan view showing the semiconductor device in adirection indicated by arrow XXVI in FIG. 24;

[0051]FIG. 27 is a top plan view showing a semiconductor device in aseventeenth preferred embodiment;

[0052]FIG. 28A is a cross-sectional view showing the semiconductordevice, taken along line XXVIIIA-XXVIIIA in FIG. 27;

[0053]FIG. 28B is a cross-sectional view showing the semiconductordevice, taken along line XXVIIIB-XXVIIIB in FIG. 27;

[0054]FIG. 29 is a diagram showing an equivalent circuit of an IGBT chipin the semiconductor device in the seventeenth embodiment;

[0055]FIGS. 30A to 30D are schematic views showing a method formanufacturing radiation members in the seventeenth embodiment;

[0056]FIG. 31 is a schematic view showing a constitution observed in aside direction in a manufacturing process of the semiconductor device;

[0057]FIGS. 32A to 32C are schematic views showing a step for caulkingfixation;

[0058]FIG. 33 is a cross-sectional view partially showing an IGBT chipas an example;

[0059]FIG. 34 is a cross-sectional view showing a semiconductor devicein an eighteenth preferred embodiment;

[0060]FIGS. 35A and 35B are cross-sectional views showing a radiationmember used in a modified example of the eighteenth embodiment; and

[0061]FIG. 36 is a cross-sectional view showing a semiconductor devicein a modified embodiment of the seventeenth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

[0062] A first preferred embodiment is described with reference to FIGS.2A and 2B. As shown in FIG. 2A, a pair of radiation members 2, 3 aredisposed to sandwich two Si chips 1 a, 1 b that are disposed on a plane.The radiation members 2, 3 are thermally and electrically connected toprincipal electrodes of the Si chips 1 a, 1 b through bonding members 4.Hereinafter, connection means thermal and electrical connection exceptcases in which specific descriptions are presented. A control electrodeof the Si chip 1 a is electrically connected to a control terminal 5,which is connected to a lead frame, via a wire 8 formed by wire bonding.

[0063] Specifically, the radiation member (first side radiation member)2, facing upper surfaces (first surfaces) 6 a of the Si chips 1 a, 1 bto which the wire bonding is performed is formed with protrudingportions 2 a protruding at a step-like shape at positions facing theprincipal electrodes of the Si chips 1 a, 1 b. Front ends of theprotruding portions 2 a are generally flat and the flat portions arerespectively connected to the principal electrodes through the bondingmembers 4. Being generally flat means flat at a level that does notinterfere with bonding between the protruding portions 2 a and theprincipal electrodes.

[0064] Next, the protruding portions 2 a are explained in more detail.As shown in FIG. 2B, when the Si chips 1 a, 2 b are power devices, eachwithstand voltage at peripheral portions of the Si chips 1 a, 1 b iskept by guard rings 7 that is provided on one surface of each chip,i.e., on the surface 6 a or a surface (second surface) 6 b opposed tothe surface 6 a.

[0065] Like the present embodiment, when metallic materials as theradiation members 2, 3 are bonded to the both surfaces of each Si chip 1a, 1 b, the radiation member 2 is bonded to the surface (the firstsurfaces in this embodiment) 6 a where the guard rings 7 are provided.However, referring to FIG. 2B, a distance indicated by an arrow B at theperipheral portions of the Si chips 1 a, 1 b, i.e., at the regions oneof which is indicated by a broken line in the figure, the first sideradiation member 2 must be electrically insulated from the guard rings 7and from the edge surfaces of the Si chips 1 a, 1 b. Therefore,insulated regions must be provided there.

[0066] Because of this, the radiation member 2 has the protrudingportions 2 a at the positions facing the principal electrodes of the Sichips 1 a, 1 b. In other words, the radiation member 2 has recessportions at the positions facing the guard rings 7 of the Si chips 1 a,1 b to avoid the high withstand regions (insulated regions).

[0067] The radiation member (second side radiation member) 3 bonded tothe other surfaces 6 b of the Si chips 1 a, 1 b has no protrudingportion, and is generally flat. That is, the second side radiationmember 3 is generally so flat that it does not interfere withmountability of the Si chips 1 a, 1 b to the radiation member 3. In therespective radiation members 2, 3, respective surfaces opposite to thesurfaces facing the Si chips 1 a, 1 b constitute radiation surfaces 10that are also generally flat and are approximately parallel to eachother.

[0068] Here, in this embodiment, the wire-bonded Si chip is an IGBT(Insulated Gate Bipolar Transistor) 1 a, while the other Si chip is aFWD (free-wheel diode) 1 b. In the IGBT 1 a, the first side radiationmember 2 is an emitter, the second side radiation member 3 is acollector, and the control electrode is a gate. As shown in FIG. 2A, thethickness of the FWD 1 b is larger than that of the IGBT 1 a. Therefore,in the first side radiation member 2, the protruding portion 2 a facingthe IGBT 1 a has a protruding amount relatively larger than that of theother protruding portion 2 a facing the FWD 1 b.

[0069] As the first side and second side radiation members 2, 3, forexample, a metallic material including Cu or Al as a main component canbe used, which has electrical conductivity and thermal conductivitylarger than those of W and Mo, and is cheaper that those. FIG. 3 is atable showing examples of metallic materials usable as the radiationmembers 2, 3. As shown in FIG. 3, the radiation members 2, 3 can be madeof one of metal “a” to metal “l”, anoxia copper, and the like. Here, forexample, metal “a” is an alloy containing, in mass ratio, Fe (iron) at2.3%, An (zinc) at 0.1%, P (phosphorous) at 0.03%, and Cu as theremainder.

[0070] The bonding members 4 are preferable to have a shear strengthsuperior to a shear stress produced by thermal stress, and to besuperior in both thermal conductivity and electrical conductivity. Assuch conductive members 4, for example, solder, brazing filler metal, orconductive adhesive can be used. The wire 8 for wire bonding can be madeof Au (gold), Al, or the like which is used for wire bonding in general.

[0071] Also, as shown in FIG. 2A, these members 1 to 5, and 8 are sealedwith resin 9 while exposing the radiation surfaces 10 of the radiationmembers 2, 3 at the opposite side of the Si chips 1 a, 1 b, and exposingsimultaneously the control terminal 5 at the opposite side of the wirebonding. The radiation surfaces 10 of the respective radiation members2, 3 serve as electrodes and perform radiation of heat simultaneously.The resin 9 preferably has a thermal expansion coefficient approximateto those of the radiation members 2, 3. For example, epoxy based moldresin can be used as such resin 9.

[0072] Further, the resin-sealed members 1 to 5 and 8 are sandwiched bya pair of outside wiring members 11 so that the radiation surfaces 10contact the outside wiring members 11. Each of the outside wiringmembers 11 is a flat plate having a portion with a plate shape or a finewire shape that is conducted to be interconnected with an outside. Theoutside wiring members 11 and the resin-sealed members 1 to 5, and 8 arefurther sandwiched by a pair of outside cooling members 13 withplate-shaped high thermal conductivity insulating substrates 12interposed therebetween. The resin-sealed members 1 to 5 and 8, theoutside wiring members 11, the high thermal conductivity insulatingsubstrates 12, and the outside cooling members 13 are fixed by volts 4or the like screwed from the outside cooling members 13.

[0073] The outside wiring members 11 may be made of any materialsprovided that they are superior in thermal conductivity and electricalconductivity. The high thermal conductivity insulating substrates 12 canbe made of, for example, one of AlN (aluminum nitride), SiN (siliconnitride), Al₂O₃ (aluminum dioxide), SiC (silicon carbide), BN (boronnitride), diamond or the like. The outside cooling members 13 isconstructed to include a radiation fin, or to be cooled by water.

[0074] According to the constitution described above, as to anelectrical path, current flow in the order of the outside wiring member11 contacting the first side radiation member 2, the first sideradiation member 2, the Si chips 1 a, 1 b, the second side radiationmember 3, the outside wiring member 11 contacting the second sideradiation member 3 or in the inverse order. As to a thermal path, heatproduced in the Si chips 1 a, 1 b is transferred to the first side andsecond side radiation members 2, 3, the outside wiring members 11, thehigh thermal conductivity insulating substrates 12, and the outsidecooling members 13, and then is radiated.

[0075] Next, a method for manufacturing the semiconductor device shownin FIGS. 2A and 2B is explained. First, the principal electrodes on thesecond surfaces 6 a of the Si chips 1 a, 1 b are bonded to the secondside radiation member 3 through the bonding members 4. Next, the controlelectrode of the Si chip 1 a and the control terminal 5 are electricallyconnected to each other by wire bonding. After that, the principalelectrodes on the first surfaces 6 a of the Si chips 1 a, 1 b are bondedto the front ends of the protruding portions 2 a of the first sideradiation member 2 by bonding members 4. Here, the protruding portions 2a of the first side radiation member 2 are formed by pressing or thelike previously.

[0076] Subsequently, a die (not show) is prepared, and the integrated Sichips 1 a, 1 b and the first side and second side radiation members 2, 3are disposed in the die and is sealed with resin. Accordingly,electrical insulation between the radiation members 2, 3 can beattained. Successively, as described above, with respect to theradiation surfaces 10, the outside wiring members 11, the high thermalconductivity insulating substrates 12, and the outside cooling members13 are disposed in this order. Then, the outside cooling members 13 arefastened with volts, so that the members 11 to 13 are fixed. Inconsequence, the semiconductor device in the present embodiment iscompleted.

[0077] According to the present embodiment, because the first side andsecond side radiation members 2, 3 are made of metallic materialcontaining Cu or Al as a main component that is superior in thermalconductivity and electrical conductivity, the semiconductor device canbe provided with improved radiation property and improved electricalconductivity. Further, because these members can be manufactured atlower cost as compared to a conventional case using W or Mo, thesemiconductor device can be provided at low cost. Furthermore, themetallic material containing Cu or Al as the main component is so softas compared to W or Mo that workability for forming the protrudingportions 2 a on the first side radiation member 2 is good.

[0078] Besides, because the protruding portions 2 a are provided on thefirst side radiation member 2 and are connected to the respectivedifferent Si chips 1 a, 1 b, the connection between the respective Sichips 1 a, 1 b and the radiation member 2 can be performedappropriately. Specifically, the protruding amounts and the shapes ofthe protruding portions 2 can be changed in accordance with thethicknesses of the Si chips 1 a, 1 b and the shapes of the principalelectrodes of the Si chips 1 a, 1 b. Because of this, the differentsemiconductor chips 1 a, 1 b can be easily accommodated in thesemiconductor device.

[0079] The radiation surfaces 10 of the radiation members 2, 3 may haveirregularities thereon or may not be parallel to each other. However, inthis embodiment, the radiation surfaces 10 are made flat andapproximately parallel to each other. This is made possible because thesurface step, i.e., the difference in thickness between the Si chips 1a, 1 b can be absorbed by the protruding portions 2 a by controlling theprotruding amounts thereof in accordance with the respective thicknessesof the Si chips 1 a, 1 b.

[0080] As a result, in the present embodiment, because the radiationsurfaces 10 are generally flat and approximately parallel to each other,when the volts are fastened to the radiation surfaces 10 with theoutside wiring members 11, the high thermal conductivity insulatingsubstrates 12, and the outside cooling members 13 interposedtherebetween, the surfaces 10 and these members 11 to 13 can be broughtin contact with each other securely and easily at the interfacesthereof.

[0081] Moreover, because the radiation surfaces 10 are approximatelyparallel to each other, a force produced by fastening the volts isuniformly applied to the members 1 to 5, 8, 9, and 11 to 13. Therefore,these members 1 to 5, 8, 9, and 11 to 13 are not damaged or destroyed bydeviation of the force, and the assembling performance can be improved.

[0082] In general, though the IGBT 1 a and the FWD 1 b are used as apair, as the distance between the IGBT 1 a and the FWD 1 b is decreased,an operation on a circuit becomes more ideal. According to the presentembodiment, because the IGBT 1 a and the FWD 1 b are disposed adjacentlyto each other in the integrally resin-sealed semiconductor device, theoperation of the IGBT 1 a can approach the ideal state in thesemiconductor device.

[0083] When the object of the invention is limited to provide asemiconductor device capable of accommodating the differentsemiconductor chips 1 a, 1 b easily, the materials for forming the firstside and second side radiation members 2, 3 are not limited to thematerials containing Cu or Al as a main component but may be otherconductive materials having electrical conductivity. That is, when theprevention of breakage of the bonding members 4 caused by thermal stressis of greater importance, the first side and second side radiationmembers 2, 3 should be made of metallic material having a thermalexpansion coefficient approximate to that of the Si chips 1 a, 1 b. Onthe other hand, when the radiation property and the electricalconductivity are of greater importance, the radiation members 2, 3should be made of metallic material containing Cu or Al as a maincomponent.

[0084] The resin 9 used in the present embodiment not only insulates theradiation members 2, 3 from each other but also reinforces the bondingbetween the radiation members 2, 3 and the Si chips 1 a, 1 b byconnecting the radiation members 2, 3 to the Si chips 1 a, 1 b.Therefore, even when the radiation members 2, 3 are made of a metallicmaterial containing Cu or Al as a main component, which has a thermalnexpansion coefficient different from that of the Si chips 1 a, 1 b, thebreakage of the bonding members 4 caused by thermal stress can berelaxed by the resin 9.

[0085] Especially when the resin 9 has a thermal expansion coefficientapproximate to that of the radiation members 2, 3, stress is applied tothe Si chips 1 a, 1 b to promote expansion and contraction similar tothose of the radiation members 2, 3 when temperature varies. Therefore,stress applied to the bonding members 4 is relaxed and generation ofstrain is restricted, resulting in improvement of reliability at theconnection portions.

[0086] Incidentally, although the second side radiation member 3 has noprotruding portion thereon in the present embodiment, it may have aprotruding portion. Thermal conductive grease or the like may be appliedto the contact faces between the outside wiring members 11 and the highthermal conductivity insulating substrates 12, and between the highthermal conductivity insulating substrates 12 and the outside coolingmembers 13 to enhance thermal bonding further.

[0087] The contact between each outside wiring member 11 and each highthermal conductivity insulating substrate 12 is preferable to be fixedby pinching as in the present embodiment in consideration of thedifference in thermal expansion coefficient between the members 11 and12. However, each radiation surface 10 and each outside wiring member 11can be connected by solder, brazing filler metal or the like becausethese members can be made of materials having thermal expansioncoefficient not largely different from each other.

[0088] The body of the first side radiation member 2 may be separatedfrom the protruding portions 2 a. For example, the protruding portions 2a may be bonded to a plate-shaped body of the member 2 by soldering,welding, or the like. The material forming the first side radiationmember 2 is not always necessary to be identical with that forming thesecond side radiation member 3. In the present embodiment, although theresin-sealing is performed by a die, the sealing may be performed bypotting without any die.

[0089] Although it is described that the resin 9 for sealing has athermal expansion coefficient approximate to those of the first side andsecond side radiation members 2, 3, the resin 9 is not limited to that,but may be other appropriate resin when there is no need to considerbonding strength between the Si chips 1 a, 1 b and the radiation members2, 3.

[0090] Although it is described in the present embodiment that the IGBT1 a and the FWD 1 b are used as the Si chips, in some cases such as thatonly one Si chip is used, or the same kind of Si chips are used, theconnecting structure between the Si chip(s) and the radiation members 2,3 is not complicated. In these cases, the protruding portions 2 a neednot be formed on one of the radiation members 2, 3. As described above,the semiconductor device having improved radiation property andelectrical conductivity can be provided by forming the radiation members2, 3 from a metallic material containing Cu or Al as a main componenthaving electrical conductivity and thermal conductivity higher thanthose of W or Mo.

Second Embodiment

[0091] A second preferred embodiment differs from the first embodimentin an inside shape of the first side radiation member 2. FIG. 4A shows asemiconductor device in the second embodiment, and FIGS. 4B to 4D arecross-sectional views partially showing various first side radiationmembers 2 and Si chips 1 a, 1 b facing the respective radiation members2. FIGS. 5A to 5C are cross-sectional views respectively taken alonglines VA-VA, VB-VB, VC-VC in FIGS. 4B to 4D.

[0092] In FIG. 4A, the first side radiation member 2 is partiallyomitted, and the cross-sectional shapes shown in FIGS. 4B to 4D areapplicable to the omitted part. FIG. 4A also omits the outside wiringmembers 11, the high thermal conductivity insulating substrates 12, andthe outside cooling members 13. Hereinafter, different portions fromthose in FIG. 2A are explained. In FIGS. 4A to 4D and 5A to 5C, the sameparts as those in FIG. 2A are indicated with the same referencenumerals, and those explanation is made simple.

[0093] As shown in FIGS. 4A to 4D and 5A to 5C, the first side radiationmember 2 has a space 15 at a portion connected to the Si chips 1 a, 1 b.The space 15 can have a lattice shape as in an example shown in FIG. 5A,be composed of several concentric circles as in an example shown in FIG.5B, and be composed of several concentric rectangles as in an exampleshown in FIG. 5C. The shape of the space 15 in a direction perpendicularto the connection surface between the radiation member 2 and the Sichips 1 a, 1 b is as shown in FIG. 4B, 4C, or 4D. That is, there arecases where the space 15 is open at the connecting portions with the Sichips 1 a, 1 b, is open at the radiation surface 10, and is closed bothat the connecting portions with the Si chips 1 a, 1 b and the radiationsurface 10.

[0094] The space 15 can be formed by, for example, cutting work. Whenthe space 15 is closed both at the connecting portions with the Si chips1 a, 1 b and the radiation surface 10 as shown in FIG. 4D, it can beformed by forming the radiation member with the space opened at theconnecting portions with the Si chips 1 a, 1 b by cutting first as shownin FIG. 4B, and then by bonding a metal plate to close the openingportions by welding or the like.

[0095] According to the present embodiment, the same effects as thosedescribed in the first embodiment can be attained. In addition, thespace 15 formed in the first side radiation member 2 increases therigidity of the radiation member 2. As a result, stress applied to theSi chips 1 a, 1 b and to the bonding members 4 can be reduced, so thatthe breakage of the Si chips 1 a, 1 b can be prevented and thereliability in the bonding between the Si chips 1 a, 1 b and theradiation member 2 can be enhanced.

[0096] The other features not described in the second embodiment aresubstantially the same as those in the first embodiment. The space 15 isexemplified in cases it extends in the thickness direction of the Sichips 1 a, 1 b; however, it may extend in a surface direction of thechips 1 a, 1 b. Further, the space 15 may be formed in the second sideradiation member 3. The space 15 needs not be formed uniformly at theportions contacting the Si chips 1 a, 1 b, and can be arrangedappropriately at required positions.

[0097] The shape of the space 15 is not limited to the examples shown inthe figures, provided that it can reduce the rigidity of the radiationmember. When the radiation members 2, 3 are made of a metallic materialincluding Cu or Al, it is easy to form the space 15 because theradiation members 2, 3 are easy to be processed.

Third Embodiment

[0098]FIG. 6 shows a semiconductor device in a third preferredembodiment, in which the outside wiring members 11, the high thermalconductivity insulating substrates 12, and the outside cooling members13 shown in FIG. 2A are omitted. Hereinafter, different portions fromthose in the first embodiment are mainly explained, and in FIG. 6, thesame parts as those in FIG. 2A are indicated with the same referencenumerals.

[0099] As shown in FIG. 6, in the third embodiment, metallic members(partially disposed metallic members) 16 made of Mo, W, Cu—Mo, or thelike having a thermal expansion coefficient approximate to that of Sichips are disposed at the portions of the first side and second sideradiation members 2, 3 facing the Si chips 1 a, 1 b. The partiallydisposed metallic members 16 can be previously formed on the radiationmembers 2, 3 by soldering, brazing, shrinkage fitting, or press-fitting.To position the partially disposed metallic members 16 with respect tothe Si chips 1 a, 1 b with high accuracy, the Si chips 1 a, 1 b and thepartially disposed metallic members 16 should be bonded by soldering,brazing, or the like, previous to the bonding between the partiallydisposed. metallic members 16 and the radiation members 2, 3 bysoldering, brazing, or the like.

[0100] According to the present embodiment, the same effects as those inthe first embodiment can be attained. In addition, because the thermalexpansion coefficient at the connecting portions between the Si chips 1a, 1 b and the first side and second side radiation members 2, 3 areapproximated to each other, thermal stress produced by a change intemperature can be reduced at the connecting portions and the bondingstrength can be enhanced. Also, the addition of the metallic members 16having the thermal expansion coefficient approximate to that of the Sichips 1 a, 1 b approaches the strain of the radiation members 2, 3 as awhole to Si, so that stress applied to the Si chips 1 a, 1 b can belowered.

[0101] Accordingly, the semiconductor device can be provided with highreliability to the bonding strengths between the Si chips 1 a, 1 b andthe radiation members 2, 3 and without breakage of the Si chips 1 a, 1 bwhile securing the same effects as those in the first embodiment.Incidentally, the other features not described in this embodiment aresubstantially the same as those in the first embodiment. The partiallydisposed metallic members 16 need not be provided at the entire regionof each radiation member 2 or 3 connected to the Si chips 1 a, 1 b. Thepartially disposed metallic members 16 should be disposed at necessarypositions appropriately. Also, in this embodiment, the space 15 may beformed in at least one of the first side and second side radiationmembers 2, 3 as in the second embodiment.

Fourth Embodiment

[0102]FIG. 7 shows a semiconductor device in a fourth preferredembodiment. This embodiment relates to a modification of the outsidewiring members 11 described in the first embodiment. Hereinafter,different portions from the first embodiment are mainly described, andin FIG. 7, the same parts as those in FIG. 2A are indicated by the samereference numerals. In FIG. 7, the high thermal conductivity insulatingsubstrates 12 and the outside cooling members 13 are omitted.

[0103] As shown in FIG. 7, conductive terminals 17 connected to theprincipal electrodes of the Si chips 1 a, 1 b are taken out of edges ofthe first side and second side radiation members 2, 3 as main electrodeterminals to be electrically connected to an outside. The conductivemembers 17 have the same function as that of the outside wiring members11 shown in FIG. 2A.

[0104] The conductive members 17 protrude from the respective radiationmembers 2, 3 from approximately the same position with respect to therespective members 2, 3 and in an approximately identical direction thatis perpendicular to the radiation surfaces 10. That is, the conductivemembers 17 are approximately parallel to each other, and accordingly canprevent a parasitic inductance described below. The root parts of theconductive members 17 are adjacent to each other. The semiconductordevice shown in FIG. 7 dispenses with the outside wiring members 11shown in FIG. 2A, and the radiation surfaces 10 contact the outsidecooling members 13 with the high thermal conductivity insulatingsubstrates 12 interposed therebetween, although they are not shown.

[0105] It is preferable that the respective radiation members 2, 3 andthe respective conductive members 17 are integrated with each other inconsideration of electrical resistance. However, when the conductivemembers 17 are separately formed and bonded to the radiation members 2,3, screwing, welding, brazing, and soldering methods are conceivable forthe bonding. At that time, the conductive members 17 can be made ofvarious materials as long as it is superior in electrical conductivity.

[0106] According to the present embodiment, the same effects as those inthe first embodiment can be exhibited. In addition, because electricalconnection with the outside can be made via the conductive members 17,it is not necessary to connect the outside wiring members 11 to theradiation surfaces 10 of the radiation members 2, 3. As a result, ascompared to the case where the outside wiring members 11 are used, thenumber of connecting interfaces in the direction in which heat istransferred is reduced to reduce heat resistance at the connectinginterfaces. Therefore, the radiating property is further improved. Inaddition, the thickness of the semiconductor device in the thicknessdirection of the Si chips 1 a, 1 b can be reduced, resulting in sizereduction of the semiconductor device.

[0107] As a more preferable configuration, in the present embodiment,the conductive members 17 are provided to be approximately parallel, toeach other at adjacent positions, and in the semiconductor device,currents flow in the respectively conductive members 17 with the sameintensity in directions inverse to each other. When currents flow in theadjacent parallel conductive members in the inverse directions to eachother, magnetic fields produced around the conductive members arecanceled with each other. As a result, the parasitic inductance can besignificantly suppressed.

[0108] Also in the present embodiment, as in the first embodiment, theradiation members are made of a metallic material containing Cu or Al asa main component when the object of the invention is to improve theradiation property and the electrical -conductivity. In this case,because workability of Cu and Al is good, the conductive members 17 canbe easily formed by pressing, cutting, or the like.

[0109] The other features not described in the present embodiment aresubstantially the same as those in the first embodiment. In the presentembodiment, although the conductive members 17 are adjacent to andapproximately parallel to each other, the conductive members 17 are notlimited to that, but may protrude from the respective radiation membersin different directions from each other. Also when the radiation members2, 3 use a material having high hardness such as W or Mo to easily sealthe several semiconductor chips with resin, the conductive members 17are preferably formed as separate members because they are difficult tobe integrally formed with the radiation members 2, 3.

Fifth Embodiment

[0110]FIGS. 8A and 8B show a semiconductor device in a fifth preferredembodiment, in which the outside wiring members 11, the high thermalconductivity insulating substrates 12, and the outside cooling members13 shown in FIG. 2A are omitted. The present embodiment differs from thefirst embodiment in the connecting method between the Si chips 1 a, 1 band the first side radiation member 2. Hereinafter, different portionsfrom the first embodiment are mainly explained and in FIGS. 8A and 8Bthe same parts as those in FIG. 2A are assigned to the same referencenumerals.

[0111] As shown in FIGS. 8A and 8B, bump-shaped bonding members 4 areuniformly provided between the principal electrodes on the principalsurfaces 6 a of the Si chips 1 a, 1 b and the first side radiationmember 2, and spaces provided among the bonding members 4 are filledwith resin 18. The resin 18 has material properties similar to those ofmetal such as good wettability, and prevents stress concentration on thebump-shaped bonding members 4. Hereinafter, the resin is referred to asRAB (Resist Assist Bonding) resin 18. The RAB resin 18 is specificallycomposed of epoxy based resin mixed with silica fillers.

[0112] To form the constitution described above, like the semiconductordevice in the first embodiment, after the Si chips 1 a, 1 b areconnected to the second side radiation member 3 and the wire bonding arecarried out, the bonding members 4 are formed in bump shapes on theprincipal electrodes of the Si chips 1 a, 1 b at the side of the firstsurfaces 6 a, and connected to the first side radiation member 2.

[0113] Successively, the RAB resin 18 is put in an injector, and isinjected into the spaces provided among the bump-shaped bonding members4. At that time, even when the resin is not injected into all the spacesdirectly, the spaces can be filled with the resin due to a capillarytube phenomenon. After that, as described above, the integrated Si chips1 a, 1 b and the radiation members 2, 3 are put in the die, and aresealed with the resin 9 integrally.

[0114] According to the present embodiment, the same effects as those inthe first embodiment can be attained. Further, the RAB resin 18 canrestrict plastic deformation of the bonding members 4. Furthermore, theRBA resin 18 can prevent cracks, which are produced in the bondingmembers 4 due to thermal stress, from progressing. That is, the RBAresin 18 strengthens the bonding between the Si chips 1 a, 1 b and thefirst side radiation member 2, and increases the reliability inconnection.

[0115] The features not described in the present embodiment aresubstantially the same as those in the first embodiment. Also in thepresent embodiment, small bumps are arranged uniformly; however, smallernumber of bumps with larger size than those in the present embodimentmay be arranged. Although the bump-shaped bonding members 4 are adoptedfor bonding the Si chips 1 a, 1 b to the first side radiation member 2in the present embodiment, they may be adopted for bonding the Si chips1 a, 1 b to the second side radiation member 3. If the mold resin 9 canbe injected into the spaces among the bumps to fill them completely, itis not necessary to inject the RBA resin 18 previously. In this case,the mold resin 9 filling the spaces among the bumps works as the RBAresin 18. The second to fourth embodiments can be applied to the presentembodiment appropriately.

Sixth Embodiment

[0116] Hereinafter, sixth to ninth embodiments are described as first tofourth modified examples of the embodiments described above, which areapplicable to the above respective embodiments, and some of which may becombined with each other to be applied to the above respectiveembodiments.

[0117] First, the sixth embodiment is explained referring to FIGS. 9A to9C. In the above embodiments, the first side radiation member 2 isformed with the protruding portions 2 a; however, as indicated by anarrow F in FIG. 2B, because the first side radiation member 2 isthickened at the protruding portions 2 a, its rigidity is increased. Thelarger the rigidity of the first side radiation member 2 is, largercompressive stress is applied to the Si chips 1 a, 1 b.

[0118] To reduce the rigidity, a method shown in FIG. 9C is conceivable,in which the first side radiation member 2 is formed by embossing asufficiently thinned metallic plate to have a protruding portion foravoiding an insulated region, and is bonded to the Si chips 1 a, 1 bwith a decreased rigidity. However, in this method, because theradiation surface 10 of the first side radiation member 2 is not flat,it is difficult to contact the outside wiring member 11 and the outsidecooling member 13.

[0119] In this connection, in this embodiment, as shown in FIGS. 9A and9B, an insulating film 20 is formed on the first side radiation member2, with an opening pattern 19 opened at regions corresponding to theinner sides of the Si chips 1 a, 1 b than the peripheral portions of thechips 1 a, 1 b where the guard rings 7 are provided. In other words, theinsulating film 20 is formed at regions corresponding to the insulatedregions in FIG. 2B, and opened at regions corresponding to the principalelectrodes of the Si chips 1 a, 1 b at the side of the first surfaces 6a.

[0120] The insulating film 20 is preferable to be close withoutpinholes, and is necessary to withstand thermal contraction of theradiation member 2. A film made of polyimide or glass is applicable tosuch an insulating film 20. When the semiconductor device in thisembodiment is manufactured, after the insulating film 20 is formed onthe radiation member 2, the Si chips 1 a, 1 b are bonded to theradiation member 2 at the side of the first surfaces 6 a. The othersteps are substantially the same as those for the semiconductor devicein the first embodiment.

[0121] According to the method described above, the guard rings 7 can beelectrically insulated from the first side radiation member 2 by theinsulating film 20. The radiation member 2 can be formed in a plateshape without a protruding portion 2 a for avoiding the guard rings 7 ofthe Si chips 1 a, 1 b. In this case, the rigidity of the radiationmember 2 can be reduced by the decreased thickness of the radiationmember 2 as far as the radiation property is allowed. As a result, thecompressive stress applied to the Si chips 1 a, 1 b can be mitigated.

[0122] When the first side and second side radiation members 2, 3 do nothave any protruding portions, it can be suitably adopted in cases of oneSi chip, and several Si chips having an identical thickness with eachother. Even when the several Si chips are different from one another inthickness, there is no problem if the difference in thickness can beabsorbed by the amounts of the bonding members 4.

[0123] The other features not described in this embodiment aresubstantially the same as those in the first embodiment. In thisembodiment, the insulating film 20 is formed on the first side radiationmember 2; however, it may be formed on the second side radiation member3. If there is a region not filled with the resin 9 for sealing, theinsulation could not be securely attained by the resin 9. However, theinsulation can be securely provided by the insulating film 20 if it isformed on the region in advance. This prevention by the insulating film20 can be applied to the case where the radiation member 2 has theprotruding portions 2 a as well.

Seventh Embodiment

[0124] Next, the seventh embodiment is described as a second modifiedexample referring to FIG. 10. In this embodiment, the electricalconnecting method between the control terminal 5 and the controlelectrode of the Si chip la differs, and FIG. 10 shows an example inwhich the present embodiment is applied to the fourth embodiment (FIG..7). Hereinafter, different portions from those in FIG. 7 are mainlydiscussed, and in FIG. 10 the same parts as those in FIG. 7 are assignedto the same reference numeral.

[0125] As shown in FIG. 10, the electrical connection between thecontrol electrode and the control terminal 5 is provided by a bump 21that is made of, for example, solder, brazing filler metal, conductiveadhesive, or the like. According to this modified example, the wirebonding step needs not be performed, and the control terminal 5 can bebonded simultaneously with the bonding between the Si chips 1 a, 1 b andthe radiation members 2, 3. Thus, the manufacturing process can besimplified. Also, wire flow of wire bond does not occur during the resinsealing.

Eighth Embodiment

[0126] Next, the eighth embodiment is described as a third modifiedexample referring to FIG. 11. In this embodiment, the locations of theradiation surfaces 10 differ. FIG. 11 is an example in which the presentembodiment is applied to the semiconductor device that is provided bycombining the first embodiment and the seventh embodiment being thesecond modified example. Hereinafter, different portions from those inFIGS. 2A and 10 are mainly described, and in FIG. 11 the same parts areassigned to the same reference numerals.

[0127] As shown in FIG. 11, in this embodiment, each of the first sideand second side radiation members 2, 3 has a wedge shaped cross-section,and the protruding portions 2 a are formed on the first side radiationmember 2. A side face of the first side radiation member 2 and a sideface of the second side radiation member 3 (disposed at a lower side inthe figure) serve as the radiation surfaces 10. The radiation surfaces10 of the first side and second side radiation members 2, 3 areapproximately perpendicular to the connecting surfaces of the radiationmembers 2, 3 being connected to the Si chips 1 a, 1 b, and are coplanarwith each other. The radiation surfaces 10 contact the outside coolingmember 13 via the high thermal conductivity insulating substrate 12, andare fixed by insulating volts 22.

[0128] According to the present embodiment, because there is no need toprepare two outside cooling members 13, the flexibility for assemblingthe semiconductor device with the outside cooling member 13 is improved.For example, the semiconductor device of the present invention isreplaceable with a conventional cooling system having a cooling part atonly one side. In addition, because the number of the high thermalconductivity insulating substrates 12 can be reduced to one, the cost ofparts can be reduced.

[0129] In the present embodiment, although the radiation surfaces 10 areperpendicular to the connecting surfaces of the radiation members 2, 3with the Si chips 1 a, 1 b, they can be attached to various types ofoutside cooling members by changing the angle appropriately. When theconductive members described in the fourth embodiment are used, theconductive members can be taken out of side faces of the radiationmembers 2, 3 different from the radiation surfaces 10.

Ninth Embodiment

[0130] Next, the ninth embodiment is explained as a fourth modifiedexample with reference to FIG. 12. This embodiment differs in the fixingmethod of the outside wiring members 11. Hereinafter, different portionsfrom those in FIG. 2A are mainly described, and the same parts as thosein FIG. 2A are assigned to the same reference numerals in FIG. 12.

[0131] As shown in FIG. 12, each four screw holes 23 a are formed in therespective first side and second side radiation members 2, 3 from theradiation surfaces 10 not to reach the Si chips 1 a, 1 b. Each of theoutside wiring members 11 has four screw holes 23 b penetrating it andcorresponding to the screw holes 23 a. Then, screws (not shown) areinserted into the screw holes 23 a, 23 b from surfaces of the outsidewiring members 11 at an opposite side of the respective radiationsurfaces 10. Accordingly, the radiation members 2, 3 and the outsidewiring members 11 are fixed together. Here, the screw holes 23 a, 23 bare formed by a drill or the like.

[0132] According to this embodiment, because the radiation members 2, 3have the screw holes 23 a not penetrating them, the screws do notcontact the Si chips 1 a, 1 b, and the screw holes 23 a, 23 b can beformed at arbitrary positions. Also, because the fixation is achieved bythe screws, even when the pressure for fixing the outside wiring members11 to the respective radiation members 2, 3 is increased, no pressure isapplied to the Si chips 1 a, 1 b. As a result, the contact resistancesbetween the radiation members 2, 3 and the outside wiring members 11 canbe reduced, and the radiation property and the electrical conductivitycan be improved.

[0133] Especially, the screw fixation can be performed at the positionsof the second side radiation member 3 immediately under the Si chips 1a, 1 b. Therefore, thermal and electrical connection between the Sichips 1 a, 1 b and the second side radiation member 3 can be secured.The thermal connections of the semiconductor device to which the outsidewiring members 11 are screwed, and the high thermal conductivityinsulating substrates 12 and the outside cooling members 13 can beprovided, for example, substantially in the same manner as in the firstembodiment. One screw hole 23 a or 23 b is sufficient for each of themembers 2, 3, and 11 to perform the fixation described above. Thisembodiment is applicable to the above embodiments except the thirdmodified example.

Tenth Embodiment

[0134] A semiconductor device in a tenth preferred embodiment isexplained with reference to FIG. 13. This embodiment is made to improvea degree of parallelization between two lead (radiation) memberssandwiching a semiconductor element therebetween. Specifically, thesemiconductor device includes an IGBT element 101 and a diode 102 thatform a circuit as semiconductor elements. The semiconductor elements101, 102 are bonded to a surface 103 a of a plate-shaped first leadmember (first conductive member) 103 made of, for example, cupper,through first soldering members 104 composed of 10 wt % Sn (tin) and 90wt % Pb (lead) and having a fusing point of 320° C. Block-shaped heatsinks 105 made of copper are respectively bonded to the semiconductorelements 101, 102 through the first soldering members 104.

[0135] On the heat sinks 105, a second lead member (second conductivemember) 107 made of copper or the like is bonded at a surface 107 athereof through second soldering members 106 having a fusing point lowerthan that of the first soldering members 104. The second solderingmembers 6 contain, for example, Sn at 90 wt % or more, and have thefusing point of 240° C.

[0136] The surface 103 a of the first lead member 103 and the surface107 a of the second lead member 107 face each other with thesemiconductor elements 101, 102 interposed therebetween, and extendapproximately in parallel with each other (for example, an inclinationbetween the lead members 103, 107 is 0.1 mm or less). Also, in thissemiconductor device, an outer lead 108 and the IGBT element 101 areelectrically connected to each other by a bonding wire 109 made of Au orAl for electrical connection with an outside.

[0137] The members 101 to 109 assembled as above are encapsulated andsealed with mold resin 110 composed of, for example, epoxy resin, andaccordingly are protected from external environment. The other surfaces103 b, 107 b of the lead members 103, 107 are exposed from the moldresin 110, and serve as radiation surfaces.

[0138] Thus, in this semiconductor device, the circuit is composed ofthe two semiconductor elements 101, 102, and the two lead members 103,107 serve as electrodes simultaneously. Signal communication between thesemiconductor elements 101, 102 and the outside is performed through thelead members 103, 107, the wire 109, and the outer lead 108. The leadmembers 103, 107 also serve as radiation members, and facilitate heatradiation by, for example, disposing cooling members (not shown) on thesurfaces 103 b, 107 b through insulating members.

[0139] Next, a method for manufacturing the semiconductor device in thepresent embodiment is explained with reference to FIGS. 14A to 14C.First, the semiconductor elements 101, 102 are bonded to the surface 103a of the first lead member 103 through the first soldering members 104.Next, the heat sinks 105 are respectively bonded to the first and secondsemiconductor elements 101, 102, also through the first solderingmembers 104. This state is shown in FIG. 14A. These integrated membersare referred to as a work 150.

[0140] Next, the surface 107 a of the second lead member 107 is bondedto the semiconductor elements 101, 102 to which the heat sinks 105 arebonded, through the second soldering members 106 having a lower fusingpoint. Specifically, as shown in FIG. 14B, the second lead member 107 isdisposed on a jig 160 with the surface 107 a facing upward, and thesecond soldering members 106 are disposed on predetermined positions ofthe surface 107 a. Then, the work 150 shown in FIG. 14A is turned over,and disposed on the surface 107 a of the second lead member 107 throughthe second soldering members 106.

[0141] Further, a plate-shaped weight 161 made of stainless or the likeis put on the other surface 103 b of the first lead member 103. The jig160 is equipped with a spacer 162 having a specific height (for example,1 mm) made of carbon or the like for determining the gap between the twolead members 103, 107. This state is shown in FIG. 14B. Then, themembers are put in a heating furnace in this state, and only the secondsoldering members 106 undergo reflow.

[0142] Accordingly, the work 150 is pressurized by the weight 161, andas shown in FIG. 14C, the second soldering members 106 are crushed andthe gap between the two lead members 103, 107 is decreased to the heightof the spacer 162. Accordingly, the degree of parallelization betweenthe two lead members 103, 107 is controlled. Incidentally, when thefusing points of the first soldering members 104 and the secondsoldering members 106 are respectively 320° C. and 240° C., a reflowtemperature is 250° C., and a load imparted from the weight 161 to thework 150 is 0.08 g/mm² in this embodiment.

[0143] The thickness of the second soldering members 106 is preferablyabout 100 μm to 300 μm. When it is too thin, the thickness forcontrolling the degree of parallelization between the two lead members103, 107 becomes insufficient. When it is too thick, the thermalconductivity between the semiconductor elements and the lead membersbecomes insufficient. Further, the second soldering members 106containing Sn at 90 wt % or more is advantageous to secure a sufficientthermal conductivity. Incidentally, after that, wire bonding with theouter lead 108 and resin molding are performed. As a result, thesemiconductor device shown in FIG. 13 is completed.

[0144] According to the manufacturing method described above, in thework 150 in which the both surfaces of the semiconductor elements 101,102 are sandwiched by the first and second lead members (radiationmembers) 103, 107 through the first and second soldering members 104,106, because the second soldering members 106 has a fusing point lowerthan that of the first soldering members 104, reflow can be performedonly to the second soldering members 106.

[0145] Then, in this state, pressure is applied from the upper side ofthe first lead member 103 (or second lead member 107), so that thesecond soldering members 106 are deformed in the sate where thesemiconductor elements 101, 102 are supported by the first solderingmembers 104. Accordingly, the degree of parallelization between the twolead members 103, 107 can be controlled. For example, the degree ofparallelization between the two lead members 103, 107 can be made equalto or less than 0.1 mm.

[0146] Thus, according to the present embodiment, the semiconductordevice having an appropriate degree of parallelization between the twomembers 103, 107 can be provided. In FIG. 13, the semiconductor devicecan dispense with the mold resin 10. In such a case, the degree ofparallelization between the two members 103, 107 can be controlledeasily.

[0147] Also, as shown in FIG. 15, the second lead member 107 can haverecess portions 107 c (for example, having a depth of about 0.1 mm) onthe surface 107 a, and the second soldering members 106 can be disposedin the recess portions 107 c. In this case, even when the secondsoldering members 106 are crushed during the reflow and pressurizationso as to extrude, the recess portions 107 c prevent the solderingmembers 106 from bulging out. Further, when the soldering members 106are composed of soldering foils, the positioning becomes easy.

[0148] The second lead member 107 may be bonded to the semiconductorelements 101, 102 through the second soldering members 106 without theheat sinks 105. The present embodiment relates to the semiconductordevice in which the semiconductor element is sandwiched by the pair ofconductive members through the soldering members, and the conductivemembers may have only one of a radiation function and an electrodefunction.

Eleventh Embodiment

[0149] In an eleventh preferred embodiment, the present invention isapplied to a semiconductor device as an electronic instrument shown inFIG. 16. The semiconductor device is, as shown in FIG. 16, composed of aheating element 201 and a pair of radiation members 202, 203 forradiating heat from the heating element 201. On a surface 201 a of theheating element 201, a first side radiation member 202 is bonded througha radiation block 204 and a bonding member 205, while on the othersurface 201 b of the heating element 201, a second side radiation member203 is bonded through a bonding member 205. That is, the radiationmembers 202, 203 sandwich the semiconductor element 201 through thebonding members 205.

[0150] In this embodiment, the heating element 201 is a powersemiconductor element such as an IGBT or a thyrister. The bondingmembers 205 are made of solder. The first side and second side radiationmembers 202, 203, and the radiation block 204 are made of Cu. Each planeshape of the members 201 to 204 is generally rectangular.

[0151] Next, a method for manufacturing the semiconductor device isexplained. First, the semiconductor element 201, the first side andsecond side radiation members 202, 203, and the radiation block 204 areprepared. Each of the first side and second side radiation members 202,203 has an area in a plane direction larger than those of thesemiconductor element.201 and the radiation block 204.

[0152] Then, after solder paste is coated to the vicinity of the centeron the surface 203 a of the second side radiation member 203, thesemiconductor element 201 is disposed thereon. Then, likewise,semiconductor paste is coated on the semiconductor element 201, and theradiation block 204 is disposed thereon. Solder paste is further coatedon the radiation block 204.

[0153] Next, as shown in FIG. 16, a jig 206 for fixing the distancebetween the first side and second side radiation members 202, 203 isprepared. The jig 206 has a pair of surfaces (parallel surfaces) 206 a,206 b parallel with each other. The jig 206 is so disposed on the secondside radiation member 203 that the surface 6 a contacts the surface 203a of the second side radiation member 203 where the semiconductorelement 201 is not disposed. Here, the jig 206 is made of a materialsuch as Al, having a thermal expansion coefficient larger than that ofthe first side and second side radiation members 202, 203 made of Cu.

[0154] Then, the first side radiation member 202 is disposed on thesolder paste applied to the radiation block 204 and on the surface 206 bof the jig 206, and a load is applied from the upper surface 202 b ofthe first side radiation member 202 by, for example, a weight 208 asrequired. Accordingly, the first side radiation member 202 is externallypressurized so that the surface 202 a of the first side radiation member202 abuts the jig 206.

[0155] After that, the members 201 to 204 laminated as above undergoreflow in this state, so that the solder paste is hardened to be solder205, and the semiconductor element 201, the radiation block 204, and thefirst side and second side radiation members 202, 203 are bondedtogether. Successively, the weight 208 is removed, and the jig 206 isremoved by pulling it in the lateral direction. As a result, thesemiconductor device in the present embodiment is completed.

[0156] According to the present embodiment, the distance between thesurfaces (inner surfaces) 202 a, 203 a of the first side and second sideradiation members 202, 203 facing the semiconductor chip 201 can becontrolled by the thickness of the jig 206. As a result, when themembers 201 to 204 are assembled with each other by lamination, there isno need to consider dimensional tolerances of the first side and secondside radiation members 202, 203. Therefore, there is no need to thickenthe solder 205 to absorb the dimensional tolerances of the first sideand second side radiation members 202, 203. In consequence, thesemiconductor device can be provided with a solder thickness decreasedas small as possible.

[0157] Besides, in general, the respective members expand by heatingduring the reflow, and contract by cooling. The change in shape causedby this expansion and contraction becomes large as the thermal expansioncoefficient becomes large. In this embodiment, because the thermalexpansion coefficient of the jig 206 is large as compared to those ofthe first side and second side radiation members 202, 203 and theradiation block 204, after the members 201 to 204 are bonded together bythe solder 205 hardened in the sate where the respective members 201 to204 expand at the reflow, the jig 206 contracts much more than the othermembers 201 to 204 when returned to a room temperature.

[0158] As a result, the gap between the surfaces 202 a, 203 a of thefirst side and second side radiation members 202, 203 becomes largerthan that between the parallel surfaces 206 a, 206 b of the jig 206.Because of this, the jig 206 can be detached readily. Also, because thedegree of parallelization between the first side and second sideradiation members 202, 203 can be controlled by the parallel surfaces206 a, 206 b of the jig 206, the degree of parallelization between thefirst side and second side radiation members 202, 203 can be securedeven when the thickness of the solder 205 is reduced.

[0159] Although the present embodiment exemplifies the case where thethermal expansion coefficient of the jig 206 is larger that those of theother members 202 to 204, if the jig 206 can be detached after themembers 201 to 204 are bonded together, the jig 206 is not limited inthe thermal expansion coefficient. The shape of the jig 206 is notlimited to that shown in the figure, but may be other shapes so long asthe jig 206 can determine the distance between the first side and secondside radiation members 202, 203.

[0160] The solder 205 is used as the bonding member, and is formed byhardening solder paste at reflow. However, the bonding may be performedby interposing solder sheets between laminated members, and fusing andhardening the solder sheets. Conductive adhesive may be usedalternatively.

[0161] The order of disposals of the semiconductor element 201, theradiation block 204, solder paste, and the jig 206 on the second sideradiation member 203 are not limited to that described above, and ischangeable provided that the constitution shown in the figure can beobtained. It is described that the jig 206 has the parallel surfaces 206a, 206 b; however, the surfaces 206 a, 206 b need not be always parallelto each other provided that the jig 206 can fix the distance between thesurface 202 a of the first side radiation member 202 and the surface 203a of the second side radiation member 203. For example, the jig 206 canhave at least three protrusions at portions contacting the first sideand second side radiation members 202, 203.

[0162] Also, although it is not shown, in a case where a pad formed onthe surface of the semiconductor element 201 is wire-bonded to a leadframe, for example, the wire bonding can be performed after the jig 206is detached from the members bonded together. In this case, if thesemiconductor element 201 is disposed in the vicinity of the edgeportion of the second side radiation member 203, there is a case wherethe wire-bonding can be performed easily; however, the shape of thesecond side radiation member 203 can be modified appropriately so thatthe wire bonding to the pad becomes easier.

[0163] Further, the following method can be considered. Specifically,after the pad of the semiconductor element 201 is wire-bonded to thelead frame by a wire, the jig 206 is disposed on the first sideradiation member to avoid the wire and the lead frame, and then thesecond side radiation member is disposed. In this state, the members 201to 204 can be bonded. The semiconductor device in this embodiment may besealed with resin. Also, the radiation members 202 to 204 may be made ofceramic substrates having metallized surfaces.

Twelfth Embodiment

[0164]FIG. 17 schematically shows a method for manufacturing asemiconductor device in a twelfth preferred embodiment. This embodimentis substantially identical with the eleventh embodiment in theconstitution of the semiconductor device, but differs in the method formanufacturing the semiconductor device. Specifically, the method forcontrolling the dimension between the surfaces 202 a, 203 a of the firstside and second side radiation members 202, 203 differs form that in thefirst embodiment. The same parts as those in the eleventh embodiment areassigned to the same reference numerals.

[0165] In this embodiment, first, the first side and second sideradiation members 202, 203, the radiation block 204, and thesemiconductor element 201 are prepared. The first side and second sideradiation members 202, 203 are formed with through holes 221, 231penetrating in the thickness direction at the respective four corners ona plane. The through holes 221, 231 receive first and second protrudingportions 261, 271 described below.

[0166] Further, first and second jigs 260, 270 are prepared. The jigs260, 270 respectively have rectangular plate portions, and in the firstjig 260, four first protruding portions 261 protrude from a surface 260a of the plate portion, and in the second jig 270, four secondprotruding portions 271 protrude from a surface 270 a of the plateportion. The first and second protruding portions 261, 271 are providedapproximately symmetrically, at inner portions than edge portions of theplate portions.

[0167] At the respective edge portions of the jigs 260, 270, protrudingportions 262, 272 for positioning respectively protrude from thesurfaces 260 a, 270 a for determining the distance between the first jig260 and the second jig 270. The protruding portions 261, 262, 271, 272have front end portions 261 a, 262 a, 271 a, 272 a each of which is agenerally flat face. The first and second jigs 260, 270 are made of, forexample, C (carbon).

[0168] Next, the surface 202 a of first side radiation member 202 isdisposed on the surface 201 a of the semiconductor device 201 throughthe radiation block 204 and solder paste. On the other surface 201 b ofthe semiconductor element 201, the second side radiation member 203 isdisposed at the side of the surface 203 a, through solder paste. Thatis, similarly to the eleventh embodiment, the second side radiationmember 203, the semiconductor element 201, and the radiation block 204are mounted through soldering paste, and the first side radiation member202 is further mounted on the radiation block 204 through solder pasteapplied.

[0169] Then, the first jig 260 is disposed with the surface 260 a facingupward, and a spring member 290 composed of a coil spring and arectangular base 291 bonded to the end of the coil spring is disposed onthe surface 260 a. The other end of the coil spring 290 may be bonded tothe surface 260 a of the first jig 260, and may not be bonded thereto.

[0170] Then, the laminated members 201 to 204 are disposed on the firstjig 260 so that the surface 203 b of the second side radiation member203 is supported by the base 290 of the coil spring 290 disposed on thesurface 260 a of the jig 260 and so that the first protruding portions261 are inserted into the holes 231 formed in the second side radiationmember 203. Then, the weight 208 is put on the surface 202 b of thefirst side radiation member 202. The second jig 270 is positioned withthe surface 270 a facing downward, is approached to the surface 202 b ofthe first side radiation member 202, and is installed so that the secondprotruding portions 271 are inserted into the holes 221 formed in thefirst side radiation member 202. Thus, the first side and second sideradiation members 202, 203, the radiation block 204, and thesemiconductor element 201 laminated as above are sandwiched by the firstand second jigs 260, 270.

[0171] Successively, the front end portions 262 a of the protrudingportions 262 formed on the first jig 260 for positioning are made abutthe front end portions 272 a of the protruding portions 272 formed onthe second jig 270 for positioning. Accordingly, a specific distancebetween the first and second jigs 260, 270 can be kept. That is, thedistance becomes the sum of the lengths of the protruding portions 262,272.

[0172] At that time, the front end portions 261 a of the firstprotruding portions 261 abut the surface 202 a of the first sideradiation member 202, and the front end portions 271 a of the secondprotruding portions 271 abut the surface 203 a of the second sideradiation member 203. Further, the first side and second side radiationmembers 202, 203 are pressurized from the surfaces 202 a, 203 a by theelastic force of the spring member 290 and the gravitational force ofthe weight 208.

[0173] Then, in the state where the respective members 201 to 204 arefixed by the first and second jigs .260, 270, solder is hardened byreflow, and the first side and second side radiation members 202, 203,the radiation block 204, and the semiconductor element 201 are bondedtogether through the solder 205. After that, the first jig 260 and thesecond jig 270 are pulled in upper and lower direction so that themembers 201 to 204 bonded together can be detached from the jigs 260,270. Thus, the semiconductor device is completed.

[0174] According to the present embodiment, the protruding portions 261,271 can respectively be made abut the surfaces 202 a, 203 a of the firstside and second side radiation members 202, 203 while keeping a constantdistance between the first and second jigs 260, 270. Accordingly, thedistance between the surfaces 202 a, 203 a of the first side and secondside radiation members 202, 203 can be controlled. That is, referring toFIG. 17, the overlapping length K of the first and second protrudingportions 261, 271 is kept constant. Also, the surfaces 202 a, 203 a ofthe first side and second side radiation members 202, 203 arerespectively supported by the four first protruding portions 261, andthe four second protruding portions 271. Therefore, the degree ofparallelization between the first side and second side radiation members202, 203 can be secured by controlling the lengths of the protrudingportions 261, 271.

[0175] Therefore, there are no need to consider the dimensionaltolerances of the first side and second side radiation members 202, 203,and no need to thicken the solder 205 for absorbing the dimensionaltolerances of the first side and second side radiation members 202, 203.The manufacturing method in this embodiment can provide a semiconductordevice in which the solder thickness is reduced as thin as possible.

[0176] Also, because the holes 221, 231 are formed in the first side andsecond side radiation members 202, 203, the front end portions 261 a,271 a of the first and second protruding portions 261, 271 suitably abutthe surfaces 202 a, 203 a of the first side and second side radiationmembers 202, 203 by penetrating the holes 231, 221. The insertions ofthe first and second protruding portions 261, 271 into the holes 231,221 formed in the second side and first side radiation members 203, 202can position the first side and second side radiation members 202, 203in the horizontal direction, i.e., the direction parallel to thesurfaces 202 a, 203 a.

[0177] Because the second side radiation member 203 is held by thespring member 290, the second side radiation member 203 can be suitablypressurized by the elasticity of the spring member 290 even when thedimensional error of the second side radiation member 203 is large. Inaddition, because the first side radiation member 202 is pressurized bythe movable weight 208, the first side radiation member 202 can besuitably pressurized even when the dimensional error of the first sideradiation member 202 is large.

[0178] Even when the radiation members 202, 203 are different from eachother in thickness, the same jigs 260, 270 as described above can beused because the pressurization can be controlled by the spring member290 and the weight 208, and because of the same reasons as describedabove involving the employments of the spring member 290 and the weight208.

[0179] More specifically, for example, in the sate shown in FIG. 17, itis assumed that solid members having high rigidity are disposed in thegap between the first side radiation member 202 and the second jig 270,and in the gap between the second side radiation member 203 and thefirst jig 260 with heights corresponding to the gaps. In this case, ifthe thicknesses of the first side and second side radiation members 202,203 are too thick, stresses applied to the first side and second sideradiation members 202, 203 can be increased by interposing them betweenthe front end portions 261 a, 271 a of the protruding portions 261, 271and the solid members. This might result in breakage of the first sideand second side radiation members 202, 203. On the other hand, if thethicknesses of the first side and second side radiation members 202, 203are too thin, the front end portions 261 a, 271 a of the protrudingportions 261, 271 could not abut the respective radiation members 202,203. To the contrary, in this embodiment, the first side and second sideradiation members 202, 203 can be pressurized suitably by adopting thespring member 290 and the weight 208.

[0180] Also, because it is so constructed that the. semiconductor devicecan be detached from the jigs 260, 270 by detaching the jigs 260, 270respectively in the upper and lower directions., the detachment is easy.The jigs 260, 270 need not have plate-like shapes, and can have variousshapes as long as the first and second protruding portions 261, 271 areprovided. To support the surfaces 202 a, 203 a of the first side andsecond side radiation members 202, 203, it is sufficient to providethree protruding portions 261 or 271 for each. The front end portions261 a, 262 a, 271 a, 272 a of the protruding portions 261, 262, 271, 272may not be flat.

[0181] The protruding portions 262, 272 for positioning may not beprovided on the respective jigs 260, 270. For example, the second sideradiation member may be formed with a long protruding portion forpositioning with a front end portion that abuts the surface 260 a of thejig 260, without forming the protruding portion for positioning on thefirst jig 260. Further, if an external apparatus or the like can fix theinterval between the jigs 260, 270, there is no need to provide theprotruding portions for positioning.

[0182] In the figure, only one semiconductor device is shown to bemanufactured; however, several semiconductor devices can be manufacturedat the same time by using first and second jigs having several pairs offirst and second protruding portions. Although the holes 221, 231 forreceiving the protruding portions 261, 271 are formed to penetrate thefirst side and second side radiation members 202, 203, notches notchedfrom the edge portions of the radiation members 202, 203 and allowingthe protruding portions 261, 271 to penetrate therein may be formed inplace of the holes 221, 231.

[0183] Otherwise, for example, the first protruding portions 261 canpass through the outside of the second side radiation member 203 bydecreasing the area of the second side radiation member 203. In thiscase, the holes 231 are not formed in the second side radiation member203. The first side radiation member 202 has the through holes 221 forallowing the second protruding portions 271 to be inserted therein.

[0184] Otherwise, the respective radiation members 202, 203 may bewarped or bent at edge portions so that the protruding portions 261, 271can pass through with the front end portions 261 a of the firstprotruding portions 261 abutting the surface 202 a of the first sideradiation member 202, and the front end portions 271 a of the secondprotruding portions 271 abutting the surface 203 a of the second sideradiation member 203.

[0185] Although the weight 208 is disposed on the first side radiationmember 202, the spring member 290 may be disposed between the surface202 b of the first side radiation member 202 and the surface 270 a ofthe second jig 270. Although the spring member 90 is composed of a coilspring in this embodiment, it may be composed of other elastic members.Further, the front end portions 261 a, 271 a of the first and secondprotruding portions 261, 271 may be brought in contact with theradiation members 202, 203 when the reflow is performed to bond themembers 201 to 204, by adopting a thermally deformable member such as ashape memory alloy, bimetal, or the like that deforms during the reflow.

[0186] As shown in FIG. 18, dispensing with the weight 208, the secondjig 270 may be formed with a through hole 273 extending in the thicknessdirection. In this case, after the laminated members are sandwiched bythe first and second jigs 260, 270, a member 281 for pressurization canbe inserted into the through hole 273 from the side of the surface 270 bof the jig 270, and pressurize the surface 202 b of the first sideradiation member 202.

[0187] Here, another method for manufacturing the semiconductor devicein this embodiment is explained. In the method described above, afterthe respective members 201 to 204 are laminated using solder paste, theyare sandwiched by the first and second jigs 260, 270. However, after thelaminated members 201 to 204 undergo reflow to be bonded by solder 205,the bonded members may be sandwiched by the first and second jigs 260,270 and undergo the reflow again. At that time, the solder hardened isfused or softened to allow the members 201 to 204 to move, and themembers 201 to 204 can be rearranged according to the dimensionsdetermined by the jigs 260, 270. In this state, the solder 205 ishardened again.

[0188] Alternatively, the state shown in FIG. 17 can be provided bydisposing the spring member 290, the base 291, the second side radiationmember 203, a solder sheet, the semiconductor element 201, a soldersheet, the radiation block 204, a solder sheet, the first side radiationmember 202, the weight 208, and the second jig 270, on the first jig 260in this order, and by performing reflow to fuse and harden the soldersheets and to bond the members 201 to 204 together.

Thirteenth Embodiment

[0189] Hereinafter, a thirteenth preferred embodiment of the presentinvention is explained with reference to FIG. 19. Semiconductor chipsused in this embodiment are a semiconductor chip in which an IGBT isformed (IGBT chip) 301 and a semiconductor chip in which a FWD(fly-wheel diode) is formed (FWD chip) 302. The semiconductor chips 301,302 are made of mainly Si and have a thickness of about 0.5 mm. In thesemiconductor chips 301, 302, element formation surfaces are referred toas main surfaces 301 a, 302 a, and the opposite surfaces are referred toas back surfaces 301 b, 302 b. An emitter electrode is formed on themain surface 301 a of the IGBT chip 301 and a collector electrode isformed on the back surface 301 b of the IGBT chip 301, though they arenot shown.

[0190] To the main surfaces 301 a, 302 a of the semiconductor chips 301,302, back surfaces 303 b of heat sinks (E heat sinks) 303 as firstconductive members are bonded through solder 304 as first bondingmembers having electrical conductivity. In the E heat sinks 303, abonding area between the IGBT chip 301 and the E heat sink 303 isapproximately the same as the area of the emitter electrode of the IGBTchip 301. Accordingly, the E heat sink 303 can contact the emitterelectrode at the area as large as possible, and be prevented fromcontacting a peripheral portion of the emitter electrode.

[0191] On the main surface 301 a of the IGBT chip 301, there exists aregion such as a guard ring that might have a problem when it is madeequipotential with the emitter electrode. If the heat sink 303 contactsthis region, the region would have the same potential as that of theemitter electrode through the heat sink 303. Therefore, the contact areaof the IGBT 301 and the E heat sink 303 is set to be approximately equalto the area of the emitter electrode of the IGBT chip 301. Accordingly,the E heat sink 303 can be bonded to the IGBT chip 301 without causingany problems.

[0192] To the back surfaces 301 b, 302 b of the semiconductor chips 301,302, a main surface 305 a of a second conductive member 305 is bonded(electrically connected) through solder 304 as second bonding members.To main surfaces 303 a of the heat sinks 303 at an opposite side of theback surfaces 303 b, a back surface 306 b of a third conductive member306 is bonded (electrically connected) through solder 304 as thirdbonding members.

[0193] The E heat sinks 303, and the second and third conductive members305, 306 can be made of metallic members having electrical conductivity.In this embodiment, the E heat sinks 303 are made of Cu, and the secondand third conductive members 305, 306 are made of Cu alloy. The secondand third conductive members 305, 306 are plate-shaped members. The Eheat sinks 303 also are plate-shaped members, but have step portions 303c as described below.

[0194] Each of the E heat sinks 303 is formed to protrude toward thethird conductive member 306 by the step portion 303 c, and has a thinportion 303 d at the side of the semiconductor chips 301, 302. The thinportion 303 d is thinned in the thickness direction of the semiconductorchip 301. Accordingly, in each of the E heat sinks 303, the bonding areabetween the E heat sink 303 and the third conductive member 6 is smallerthan that between the E heat sink 303 and the semiconductor chip 301 or302.

[0195] Besides, a surface treatment such as Ni plating is performed tothe surface portions of the E heat sinks 303 where it is bonded to therespective semiconductor chips 301, 302 and the third conductive members306 to improve wettability of the solder 304. The other outer surfacesof the E heat sinks 303 for contacting a sealing member described beloware oxidized. The second and third conductive members 305, 306 areplated with Ni at entire outer surfaces thereof. In the second and thirdconductive members 305, 306 and the E heat sinks 303, the thickness ofthe thickest portion is about 1 mm, and the thickness of the thinportion is about 0.4 mm.

[0196] A land (not shown) is formed on the main surface of the IGBT chip301, and is electrically connected to a control terminal 307 of a leadframe via a bonding wire 308. Then, the semiconductor chips 301, 302,the E heat sinks 303, the main surface 305 a of the second conductivemember 305, the back surface 306 b of the third conductive member 306,and a part of the control terminal 307 are integrally sealed with resin309 as a sealing member. Used as the resin 309 is, for example, epoxybased mold resin. Accordingly, a the members 301 to 308 are integrallysealed to have the back surface 305 b of the second conductive member305, the main surface 306 a of the third conductive member 306, and apart of the control terminal 307 that are exposed from the resin 9.

[0197] Thus, the semiconductor device in this embodiment is constructed.In this semiconductor device, heat generated from the semiconductorchips 301, 302 is transferred to the E heat sinks 303, and to the secondand third conductive members 305, 306 through the solder 304, and thenis radiated from the back surface 305 b of the second conductive member305 and the main surface 306 a of the third conductive member 306.

[0198] When cooling members or the like are disposed to abut the backsurface 305 b of the second conductive member 305 and the main surface306 a of the third conductive member 306, heat radiation can be furtherfacilitated. Here, the E heat sinks 303 and the second and thirdconductive members 305, 306 form electrical paths for the respectivesemiconductor chips 301, 302. That is, the electrical communication withthe collector electrode of the IGBT chip 301 is provided through thesecond conductive member 305, while the electrical communication withthe emitter electrode of the IGBT chip 301 is provided through thesecond conductive member 306 and the E heat sink 303.

[0199] As explained above, in the present embodiment, each of the E heatsinks 303 bonded to the surfaces 301 a, 302 a of the semiconductor chips301, 302 has the step portion 303 c and accordingly has the thin portion303 d. Because the thin portion 303 d has small rigidity, the thinportion 303 d can follow deformation of the resin 309 surrounding it andcan absorb thermal stress when the semiconductor device undergoesthermal cycle. Therefore, stress concentration on the solder 304 bondingthe semiconductor chips 301, 302, and the E heat sinks 303 can bemitigated.

[0200] In general, the smaller the bonding area of solder is, thesmaller the bonding strength of the solder becomes. Therefore, in eachof the E heat sinks 303, the bonding area with the third conductivemember 306 is set to be smaller than that with the semiconductor chip301 or 302. Accordingly, cracks become liable to be produced in thesolder 304 bonding the E heat sink 303 and the third conductive member306.

[0201] As a result, when thermal stress is increased, cracks areproduced first in the solder 304 bonding the E heat sink 303 and thethird conductive member 306 to mitigate thermal stress, and accordinglythermal stress applied to the solder 304 bonding the E heat sink 303 andthe semiconductor chip 301 or 302 can be lessened.

[0202] Incidentally, even when cracks are produced in the solder 304bonding the E heat sink 303 and the third conductive member 306 as aresult of stress concentration, because both the E heat sink 303 and thethird conductive member 306 include Cu as a main component, thosedeformations caused by the thermal cycle are approximated to each otherand cracks do not advance largely in the solder 304. Even if the cracksadvance, because the current path is formed by the entire bondingsurface between the E heat sink 303 and the third conductive member 306,significant problems do not occur.

[0203] Further, because the surface portions of the E-heat sink 303 forcontacting the resin 309 are oxidized, adhesion with the resin 309 canbe improved. As a result, the deformation of the resin 309 caused bythermal stress and the deformation of the E heat sink 303 synchronizewith each other, and stress concentration on the solder 304 bonding theE heat sink 303 and the semiconductor chip 301 or 302 can be mitigated.Incidentally, adhesion between Cu alloy and the resin 309 is improved byplating the Cu alloy with Ni. Therefore, the surfaces of the second andthird conductive members 305, 306 are plated with Ni instead ofoxidation.

[0204] Thus, thermal stress concentration to the solder 304 bonding therespective semiconductor chips 301, 302 and the E heat sinks 303 can besuppressed, so that cracks can be prevented to reach this solder 304.Even when several cells are formed on the main surface (elementformation surface) 301 a of the IGBT chip 301, current is prevented fromconcentrating on a cell provided at the center, and breakage of the cellis prevented.

[0205] Also, because each of the E heat sinks 303 has the step portion303 c, as compared with a case of adopting a prism shape heat sinkwithout a step portion, a creepage distance from the interface betweenthe third conductive member 306 and the resin 309 to the bonding portionbetween the semiconductor chip 301 or 302 and the E heat sink 303 islong. Because of this, it can be retarded that cracks produced at theinterface between the third conductive member 306 and the resin 309reach the bonding portion between the semiconductor chip and the E heatsink 303.

[0206] With respect to the semiconductor device according to thisembodiment, a thermal shock cycle test was performed, in which thesemiconductor device was exposed to environments of −40° C. and 125° C.respectively for 60 minutes, a resistance between the third conductivemember 306 and the control terminal 307 was measured, and a rate ofchange in resistance was calculated using an initial value as areference. Then, it was confirmed that the rate of change in resistancedid not increase largely even at 200 cycles. It was further confirmedthat the rate in change of resistance of the semiconductor device inthis embodiment was small as compared to a case where the heat sink hadno step portion.

[0207] Next, a method for manufacturing the semiconductor device in thisembodiment is explained with reference to FIGS. 20A to 20C. First, thesecond and third conductive members 305, 306 are formed from plates madeof cupper alloy or the like by punching. After that, the entire outersurfaces of the second and third conductive members 305, 306 are platedwith Ni.

[0208] Cu plates are prepared for forming the E heat sinks 303. Niplating is performed to both the main and back surfaces of each Cuplate. After that, Cu members having a size corresponding to the E heatsinks 303 are formed from the Cu plates plated with Ni, by punching orthe like. Then, each of the Cu members is pressed to have the stepportion 303 c. Thus, the E heat sinks 303 are completed. Each of the Eheat sinks 303 has portions plated with Ni for being bonded to thesemiconductor chip 301 or 302 and to the third conductive member 306,and portions exposed by punching and not plated with Ni. At the exposedportions, plating is peeled off by pressing.

[0209] As shown in FIG. 20A, the semiconductor chips 301, 302 are bondedto the main surface 305 a of the second conductive member 305 throughthe solder 304. Next, the E heat sinks 303 are bonded to the respectivesemiconductor chips 301, 302 through the solder 304. The solder 304 usedfor bonding the semiconductor chips 301, 302 and the second conductivemember 305, and the E heat sinks 303 has a relatively high fusing point.For example, solder composed of 10 wt % Sn (tin) and 90 wt % Pb (lead)and having a fusing point of 320° C. (high temperature solder) can beused as the solder 304. Accordingly, the state shown in FIG. 20A isprovided, which is referred to as a work 310.

[0210] Next, as shown in FIG. 20B, the third conductive member 306 isput on a jig 311 with the back surface 306 b facing upward, and solder 4is disposed on desirable regions of the back surface 306 b. Then, thework 310 shown in FIG. 20A is turned over, and is disposed on the thirdconductive member 306. The solder 4 interposed between the thirdconductive member 306 and the semiconductor chips 301, 302 has a fusingpoint lower than that of the high temperature solder described above.For example, solder containing Sn at 90 wt % or more and having a fusingpoint of 240° C. can be used as the solder 4. Hereinafter, this solderis referred to as low temperature solder.

[0211] Further, a plate-shaped weight 312 is disposed on the backsurface 305 b of the second conductive member 305. Here, the jig 311 hasa spacer 313 having a predetermined height for fixing the distancebetween the second and third conductive members 305, 306. This state isshown in FIG. 20C. In this state, it is put into a heating furnace, andreflow is performed only to the low temperature solder 4. As a result,the work 310 is pressurized by the weight 312, and as shown in FIG. 20C,the low temperature solder 4 is crushed so that the distance between theback surface 306 b of the third conductive member 306 and the mainsurface 305 a of the second conductive member 305 corresponds to theheight of the spacer 313. Accordingly, the degree of parallelizationbetween the second and third conductive members 305, 306 can beadjusted.

[0212] Also, the E heat sinks 303 are bonded to the respectivesemiconductor chips 301, 302 in the state where the E heat sink 303contacts only the emitter electrode on the IGBT chip 301 by the hightemperature solder 304, and are bonded to the third conductive member306 by the low temperature solder 304. Therefore, when the heat sinks303 are bonded to the third conductive member 306, the high temperaturesolder 304 does not fuse, and the bonding positions of the E heat sinks303 to the semiconductor chips 301, 302 can be appropriately maintained.Incidentally, when the fusing points of the high temperature solder 304and the low temperature solder 304 are respectively 320° C. and 240° C.,the reflow temperature for the low temperature solder 304 is preferably250° C.

[0213] After that, although it is not shown, the control terminal 307and the IGBT chip 301 are electrically connected to each other by thebonding wire 308, and the members 301 to 308 are sealed with resin 309as shown in FIG. 19. This resin sealing is performed by injecting theresin 309 having a temperature of about 180° C. into spaces providedamong the members 301 to 308. At that time, the surface portions of theE heat sinks 303 exposing copper and not bonded to either of thesemiconductor chips 301, 302 and the third conductive member 306 areoxidized. Thus, the semiconductor device is completed.

[0214] In general, when Ni plating is performed to the E heat sink,after the E heat sink is formed into the shape capable of being disposedbetween the semiconductor chip and the third conductive member, the Eheat sink is put in a plating machine, and an entire area of the outersurface of the E heat sink is plated. Therefore, the solder disposed onthe E heat sink can easily wet and expand to the region other than thebonding portions with the semiconductor chip and the third conductivemember.

[0215] In addition, the thickness of the E heat sink 303 is thin, i.e.,about 1 mm, the low temperature solder 304 and the high temperaturesolder 304 are located at close positions to each other. If the Niplating is performed to the entire outer surface of the E heat sink 303,there arises a case where the low temperature solder 304 and the hightemperature solder 305 are mixed with each other. As a result, eutecticsolder having a fusing point much lower than that of the low temperaturesolder 304 might be formed, which can fuse at the temperature (forexample, 180° C.) for sealing the members 301 to 308 with the resin 309.

[0216] As opposed to this, in the present embodiment, Ni plating isperformed only to the portions of the E heat sink 303 for bonding thesemiconductor chip 301 or 302 and the third conductive member 306. Thelow temperature solder 304 and the high temperature solder 304 aredisposed with the oxide surface of Cu interposed therebetween. Becausethe wettability of the oxide surface of Cu to the solder 304 is low, thehigh temperature solder 304 and the low temperature solder 304 do notexpand to other regions than the bonding portions, and do not mix witheach other. Incidentally, although solder is used as the bonding members(first to third bonding members) in this embodiment, Ag paste or thelike can be used alternatively. The bonding members need not be alwaysan identical material with one another.

Fourteenth Embodiment

[0217]FIG. 21 shows a semiconductor device in a fourteenth preferredembodiment. The fourteenth embodiment differs from the thirteenthembodiment in the shape of the third conductive member 306. Hereinafter,different portions from the thirteenth embodiment are mainly explained.In FIG. 21, the same parts as those in FIG. 19 are assigned to the samereference numerals, and the same explanations are not reiterated.

[0218] As shown in FIG. 21, a step portion 306 c is formed on the mainsurface 306 a of the third conductive member 306. Then, the step portion306 c is covered with the resin 309 for sealing. Accordingly, creepagedistances from the interface between the resin 309 and the thirdconductive member 306 to the bonding portions of the E heat sinks 303with the semiconductor chips 301, 302 on the surface of thesemiconductor device can be further increased as compared to those inthe first embodiment. As a result, cracks are further suppressed frombeing produced in the solder 4 bonding the semiconductor chips 301, 302and the E heat sinks 303.

[0219] Incidentally, the creepage distances can be further increased asthe area covered with the resin 309 on the surface 306 a of the thirdconductive member 306 is increased. However, the decreased exposed areaof the third conductive member 306 deteriorates the radiation property.Therefore, the third conductive member 306 should be covered with theresin 309 at a degree not to deteriorate the radiation property.

Fifteenth Embodiment

[0220]FIG. 22 shows a semiconductor device in a fifteenth preferredembodiment. This embodiment differs from the thirteenth embodiment in apoint that conductive members are disposed between the respectivesemiconductor chips 301, 302 and the second conductive member 305.Hereinafter, portions different from the thirteenth embodiment aremainly described. In FIG. 22, the same parts as those in FIG. 19 areassigned to the same reference numerals.

[0221] As shown in FIG. 22, collector heat sinks (C heat sinks) 314 aredisposed between the second conductive member 305 and the respectivesemiconductor chips 301, 302, at the side of the back surfaces 301 b,302 b of the semiconductor chips 301, 302. The C heat sinks 314 hasareas approximately the same as those of the corresponding semiconductorchips 301, 302 in a direction perpendicular to the thickness directionof the semiconductor chips 301, 302.

[0222] Specifically, surfaces (main surfaces) 314 a of the C heat sinks314 are respectively bonded to the back surfaces 301 b, 302 b of thesemiconductor chips 301, 302 through the solder 304. Back surfaces 314 bof the C heat sinks 314 are bonded to the main surface 305 a of thesecond conductive members 305 through the solder 304.

[0223] The second conductive member 305 has a relatively large area withrespect to its thickness, and therefore has a possibility that it isbent (warped). On the other hand, when the injection of the resin 309 isperformed, the back surface 305 b of the second conductive member 305and the main surface 306 a of the third conductive member 306 arepinched under relatively large pressure to prevent leakage of the resin309. Therefore, if the second conductive member 305 holding thesemiconductor chips 301, 302 is bent, the pressure pinching the secondand third conductive members 305, 306 during the sealing canmechanically cause damages to the semiconductor chips 301, 302.

[0224] As opposed to this, in this embodiment, the C heat sinks 314 aredisposed on the back surfaces 301 b, 302 b of the semiconductor chips301, 302, and the C heat sinks 314 are smaller than the secondconductive member 305 in size. Therefore, the bending can be suppressedand the semiconductor chips 301, 302 can be securely prevented frombeing damaged. Thus, this embodiment can prevent the mechanical damageto the semiconductor chips 301, 302, in addition to the effects asattained in the thirteenth embodiment. Incidentally, in the constitutiondescribed in the fourteenth embodiment in which the third conductivemember 306 has the step portion 306 c that is covered with the resin309, the C heat sinks 314 can be disposed as well.

[0225] In the thirteenth to fifteenth embodiments described above, the Eheat sinks 303 respectively have the thin portions 303 d at the side ofthe semiconductor chips 301, 302; however, as shown in FIG. 23, the stepportions 303 d may be provided at the side of the third conductivemember 306. Also in this constitution, thermal stress can be preventedfrom concentrating on the solder 4 at the bonding portions between thesemiconductor chips 301, 302 and the heat sinks 303 by the low rigiditythin portions 303 d that can absorb the thermal stress, as compared tothe case where the E heat sinks have a prism-like shape.

[0226] In the thirteenth to fifteenth embodiments described above, ineach of the E heat sinks 303, the step portion 303 c is provided at anentire portion contacting the resin 309; however, with respect to thesolder 304 bonding the semiconductor chips 301, 302 and the E heat sinks303, cracks progress from the periphery side of the resin 309 toward thecenter. Therefore, the step portion 303 c may be provided only at theportion facing the outer periphery of the resin 309. Here, the peripheryof the resin 309 means a periphery of a portion surrounding the secondand third conductive members 305, 306, and in FIG. 19 it corresponds asurface approximately parallel to the thickness direction of thesemiconductor chips 301, 302.

Sixteenth Embodiment

[0227]FIG. 24 shows a semiconductor device in a sixteenth preferredembodiment. In this embodiment, an IGBT 411 and a FWD (free-wheel diode)412 each of which is made of a Si substrate are used as semiconductorchips. At a side of each element formation surface (first surface) 401 aof the IGBT 411 and the FWD 412, first side and second side radiationmembers 421, 422 are bonded through solder 431. A third radiation member423 is further bonded to the first side and second side radiationmembers 421, 422 through solder 432 at an opposite side of the chips411, 412. The first to third radiation members 421 to 423 are made of,for example, Cu and constitute a first side radiation member 420.

[0228] The third radiation member 423 is a plate having a protrudingportion 423 b, and has a generally L-shape cross-section with theprotruding portion 423 b as a short side in a thickness directionthereof. The first side and second side radiation members 421, 422 arebonded to a long side of the L-shape of the third radiation member 423.The protruding portion 423 b has a front end portion 423 a tat isapproximately coplanar with second surfaces 401 b of the chips 411, 412at an opposite side of the first surfaces 401 a.

[0229] Besides, a DBC (Direct Bonding Cupper) substrate 404 is disposedas a high thermal conductivity insulating substrate at a side of thesecond surfaces 401 b of the chips 411, 412. The DBC substrate 404 iscomposed of an AlN (aluminum nitride) substrate 405 both first andsecond surfaces 405 a, 405 b of which are patterned with copper foils451 to 454. The second surfaces 401 b of the chips 411, 412 arerespectively bonded to a first copper foil 451 on the first surface 405a of the DBC substrate 404, through solder 433. Further, the front endportion 423 a of the protruding portion 423 b of the third radiationmember 423 is bonded to the second copper foil 452 of the DBC substrate404, through solder 434.

[0230] Next, the electrode (wiring) portion of the IGBT 411 is explainedwith reference to FIG. 25 showing a part surrounded by a broken line inFIG. 24. As shown in FIG. 25, a barrier metal 111 is formed on asubstrate 100 of the IGBT 411 at the side of the first surface 401 a. Anemitter electrode 112 and a land 113 for wire bonding are further formedfrom pure Al. The barrier metal 111 is composed of Ti (titanium) and TiN(titanium nitride) which are formed on the substrate 100 at this order,and has a thickness of about 0.1 μm. The thickness of the electrode 112,113 is about 5 μm.

[0231] Further, a metallic film 114 is formed on the emitter electrode112 to be suitably connected with the solder 431. The metallic film 114is composed of Ti, Ni (nickel), and Au (gold) formed from the side ofthe emitter electrode 112 sequentially, and has a total thickness ofabout 0.6 μm. To this metallic film 114, as described above, the firstside radiation member 421 is bonded through the solder 431. Here, thethicknesses of the solder 431 and the first side radiation member 421are, for example, about 0.1 mm and about 1.5 mm respectively.

[0232] On the other hand, at the side of the second surface 401 b of thesubstrate 100, a collector electrode 115 made of pure Al is formedwithout barrier metal. The collector electrode 115 is, for example,about 0.2 μm in thickness. A metallic film 116 is then formed on thecollector electrode 115, similarly to the emitter electrode 112. Themetallic film 116 is bonded to the first cupper foil 451 on the firstsurface 405 a of the DBC substrate 404 through the solder 433.Incidentally, the electrode portion of the FWD 412 has a structuresubstantially the same as that of the IGBT 411.

[0233] Further, as shown in FIGS. 24 and 25, the third radiation member423 is electrically connected to a lead 461 by a connection terminal 406a for electrically connecting the emitter electrode 112 and the lead(emitter terminal) 461 as an outside terminal. On the DBC substrate 404,a land 453 is formed, and is wire-bonded to the land 113 on the surface401 a of the IGBT 411 by a wire 407. The land 453 of the DBC substrate404 is further wire-bonded to a gate terminal 408 by another wire 407.As the wires 407, Au, Al, or the like used generally for wire bondingcan be used. The land 453 of the DBC substrate 404 is provided for anintermediation between the land 113 and the gate terminal 308.

[0234] To the copper foil 454 formed on the back surface 405 b of theDBC substrate 404, a fourth radiation member (second side radiationmember) 424 is bonded through solder 435. That is, the first sideradiation member 420 and the second side radiation member 424 are joinedtogether with the DBC substrate 404 interposed therebetween, andelectrical insulation and electrical conductivity of the respectiveradiation members 420, 424 can be secured respectively.

[0235] Then, the members described above are sealed with resin 400 sothat the fourth radiation member 424 has a radiation surface 409 exposedat an opposite side of the surface bonding the DBC substrate 404. Forexample, epoxy based mold resin can be used as the resin 400.

[0236] Next, the electrical connection in each part of the semiconductordevice in this embodiment is explained in more detail, referring to FIG.26 that shows the semiconductor device in a direction indicated by arrowXXVI in FIG. 24. Incidentally, FIG. 24 shows a cross-section taken alongline XXIV-XXIV in FIG. 26. The semiconductor device holds two pairs ofthe IGBT 411 and the FWD 412 in this embodiment.

[0237] The first side radiation member 420 (421 to 423) is indicatedwith a one-dot chain line in the figure, and as described above, iselectrically connected with the emitter terminal 461 through theconnection terminal 406 a. The first copper foil 451 of the DBCsubstrate 404 is bonded to all of the electrodes on the surfaces 401 bof the IGBTs 411 and the FWDs 412, and has a protruding portion 451 aprotruding not to contact the second cupper foil 452 of the DBCsubstrate 404. The protruding portion 451 a is electrically connected tothe collector terminal 462 as a lead through a connection terminal 406b.

[0238] In this semiconductor device, the radiation surface 409 is fixedto a radiation fin (not shown) as a cooling member (outside radiator) byscrewing or the like. Accordingly, heat generated from the firstsurfaces 401 a of the chips 411, 412 is radiated from the radiationsurface 409 through the first side radiation member 420, the DBCsubstrate 404, and the second side radiation member 424. That is, theradiation direction from the first surfaces 401 a of the chips 411, 412corresponds to the direction extending from the first surfaces 401 a tothe second surfaces 401 b in the respective chips 411, 412 (from theupper side to the lower side in FIG. 24).

[0239] On the other hand, heat generated from the second surfaces 401 bof the chips 411, 412 is also radiated from the radiation surface 409through the DBC substrate 404 and the second side radiation member 424.Thus, in the semiconductor device in which the chips are mounted,radiation of heat from both the surfaces 401 a, 401 b of the chips 411,412 is performed mainly by the same radiation surface 409.

[0240] Next, a method for manufacturing the semiconductor device in thisembodiment is explained. First, as describe above, the IGBT 411 havingthe barrier metal 111, the emitter electrode 112, the collectorelectrode 115, the metallic films 114, 116, and the like and the FWD 412are prepared. The electrodes 112, 115, the barrier metal 111, themetallic films 114, 116, and the like are formed by sputtering or thelike. Then, the first side and second side radiation members 421, 422are soldered to the first surfaces 401 a of the chips 411, 412.

[0241] Next, the DBC substrate 404 having the first and second surfaces405 a, 405 b on which the cupper foils 451 to 454 are patterned isprepared, and the IGBT 411 and the FWD 412 are soldered to predeterminedportions of the DBC substrate 404. After that, the third radiationmember 423 is soldered not only to the first side and second sideradiation members 421, 422 but also to the DBC substrate 404. Whensoldering the third radiation members 423, a thickness of solder isthickened at the bonding portion with the DBC substrate 404 as comparedto that with the first side and second side radiation members 421, 422,and accordingly, variations in thickness by soldering is absorbed.

[0242] These soldering can be performed by reflow or the like. Whenkinds of solder used in this method are changed so that fusing points ofsolders are decreased in the order of the soldering, the soldering canbe sufficiently performed without affecting the solder that has beensoldered first. Then, the emitter terminal 461 and the collectorterminal 462 are connected to the third radiation member 423, and theIGBT 411 and the gate terminal 408 are wire-bonded to each other.Successively, the fourth radiation member 424 is soldered to the DBCsubstrate 404, and finally resin sealing is performed.

[0243] According to the present embodiment, because an elastic modulusof pure Al is small, thermal stress produced due to differences amongthe chips 411, 412 and the radiation members 421 to 424 can bemitigated. Specifically, the elastic modulus of pure Al is 72 GPa, andan elastic modulus of Al containing Si at 1% is about 75 GPa. When theAl containing Si is used, Si may be segregated. In such a case, becausethe elastic modulus of Si is 130 GPa, the capability for mitigatingthermal stress is locally but significantly decreased.

[0244] As opposed to this, in this embodiment, especially because theemitter electrode 112 of the IGBT 411 is made of pure Al, stress isprevented from concentrating on the emitter cell, and fluctuation inelectrical characteristics such as Vt can be suppressed. Therefore, thechip and the semiconductor device can be provided with high electricalreliability. Also, because the electrodes on the second surfaces 401 bof the chips 411, 412 are made of pure Al, the chips 411, 412 areprevented from being warped due to thermal stress.

[0245] Also, because Si is not contained in the electrodes 112, 113,115, deposition of Si nodule can be prevented. This is especiallyeffective for the land 113 for wire. bonding because Si nodule can causecracks in the device by vibrations (stress) produced by wire-bonding.Thus, externally applied stress can be mitigated by forming theelectrodes 112, 113, 115 from pure Al.

[0246] However, when the pure Al is brought in direct contact with thesubstrate 100 made of Si, ally spikes are produced. Therefore, thebarrier metal 111 is disposed between the electrodes 112, 113 and thesubstrate 100, and prevents the generation of alloy spikes.Incidentally, the barrier metal is not formed on the other surface 401 bof the IGBT 411. This is because even when alloy spikes are produced onthe other surface 401 b, the alloy spikes do not reach the device formedat the side of the surface 401 a.

[0247] In the semiconductor device in which a chip is sandwiched by apair of radiation members respectively having radiation surfaces,cooling members sandwich the semiconductor device to contact theradiation surfaces respectively. However, in this constitution, stressproduced when the cooling members sandwiche the semiconductor device isliable to be concentrate on the chip.

[0248] As opposed to this, in this embodiment, the radiation surface 409for radiating heat to the outside of the semiconductor device is formedat one side (the side of the second surfaces 401 b) of the chips 411,412. In this constitution, the semiconductor device needs not besandwiched by the cooling members for radiating heat. Therefore, evenwhen the radiation surface 409 is firmly bonded to the outside coolingmember, large stress is not applied to the chips 411, 412.

[0249] Especially, because the radiation surface 409 is provided at theside of the second surfaces 401 b of the chips 411, 412, stress isprevented from concentrating on the first surfaces 401 a of the chips411, 412, and the fluctuations in electric characteristics of the deviceprovided at the first surface side can be securely prevented.

[0250] Further, because both surfaces 401 a, 401 b of the chips 411, 412are bonded to the radiation members 421, 422, 424, respectively, theradiation of heat is performed from both surfaces 401 a, 401 b of thechips 411, 412. Therefore, the radiation property is also sufficient.

[0251] Furthermore, the radiation surface 409 is electrically insulatedfrom the chips 411, 412 by the DBC substrate 404 that is an insulatingsubstrate disposed inside the semiconductor device. Therefore, there isno need to consider electrical insulation when the radiation surface 409is bonded to the outside cooling member. Also, the one insulatingsubstrate 404 can secure electrical insulation from both the first andsecond surfaces 401 a, 401 b of the chips.

[0252] In this embodiment, although the radiation surface 409 isprovided at the side of the second surfaces 401 b of the chips 411, 412,the other portion can assist the radiation of heat. For example, thethird radiation member 423 may be partially exposed from the resin 400to assist the radiation of heat. The electrode 115 formed on the secondsurfaces 401 b of the chips 411, 412 needs not be made of pure Al toprotect the devices of the chips 411, 412. The first to third radiationmembers 421 to 423 are separate members, and are integrally bonded toform the first side radiation member 420 by soldering in thisembodiment; however, they may be formed as an integrated member.

[0253] The electrodes for the FWD 412 need not be formed from pure Al ifno problem occurs concerning thermal stress or the like. When the firstside radiation member 420 needs not be electrically insulated from thesecond side radiation member 424, the DBC substrate 404 made of AlN canbe omitted. The DBC substrate 404 can dispense with the land 453 if theland 113 of the IGBT 411 can be wire-bonded to the gate terminal 408directly.

Seventeenth Embodiment

[0254] A semiconductor device in a seventeenth preferred embodiment isshown in FIGS. 27, 28A and 28B. As shown in the figures, in thisembodiment, first side and second side radiation members 503, 504 arebonded to two Si chips 501 a, 501 b, which are arranged on a plane,through a bonding member 502 having thermal conductivity to sandwich thechips 501 a, 501 b.

[0255] The first side radiation member 503 is boned to surfaces (firstsurfaces) 505 a of the Si chips 501 a, 501 b to which wire bonding isperformed, and the second side radiation member 504 is bonded to theother surfaces (second surfaces) 505 b of the Si chips 501 a, 501 b atan opposite side of the surfaces 505 a. In FIG. 27, portions of thesecond side radiation member 504 where it overlaps with other membersare indicated with two-dot chain lines, and portions of the Si chips 501a, 501 b where they overlap with other members are indicated withone-doe chain lines.

[0256] In this embodiment, the Si chip wire-bonded in FIG. 27 is an IGBTchip 501 a, and the other Si chip is a fly-wheel diode chip 501 b. Inthe IGBT chip 501 a, the first side radiation member 503 serves as anemitter terminal, and the second side radiation member 504 serves as acollector terminal. On the surface of the IGBT chip 501 a facing thefirst side radiation member 503, a control electrode (not shown) forgiving or receiving electrical signals to or from an external is formed,and is wire-bonded to an inner lead 510.

[0257] An equivalent circuit of the IGBT chip 501 a is, for example asshown in FIG. 29, which is composed of a collector C, an emitter E, agate G, a current detection terminal Is, an anode A that is a diodeterminal for thermosensitivity, and a cathode K.

[0258] As shown in FIGS. 27, 28A, and 28B, the plane shape of the firstside radiation member 503 is substantially a rectangle and has stripportions 503 a, 503 b respectively extending from opposite corners ofthe rectangle in opposite directions to each other. Besides, the firstside radiation member 503 has convex portions (protruding portion) 506respectively protruding in a thickness direction thereof to faceprincipal electrodes of the Si chips 501 a, 501 b at the side of thesurfaces 505 a. Front ends of the convex portions 506 are flat at alevel that does not interfere with bonding with the Si chips 501 a, 501b, and the shapes of the flat front ends correspond to plane shapes ofthe principal electrodes of the Si chips 501 a, 501 b.

[0259] Besides, on the surface of the first side radiation member 503facing the Si chips 501 a, 501 b, protruding portions 507 a are providedat three locations that are at the strip portions 503 a, 503 b and at aninside of one side parallel to the directions in which the stripportions 503 a, 503 b extend. The protruding portions 507 a protrudetoward the side of the Si chips 501 a, 501 b.

[0260] The second side radiation member 504 is approximately the same asthe first side radiation member 503, but has two strip portions 504 athat are provided at different locations from those of the stripportions 503 a of the first side radiation member 503. In the thicknessdirection, concave portions 508 are provided to fitly accommodate the Sichips 501 a, 501 b. The depths of the concave portions 508 are about 0.1to 0.3 mm.

[0261] Further, the surface of the second side radiation member 504facing the Si chips 501 a, 501 b has protruding portions 507 bprotruding toward the side of the Si chips 501 a, 501 b at threelocations that are at the strip portions 504 a, 504 b, and at an insideof one side parallel to the directions in which the strip portions 504a, 504 b extend. The protruding portions 507 b of the second sideradiation member 504 are positioned not to overlap with the protrudingportions 507 a of the first side radiation member 503 when they areobserved in an upper direction as shown in FIG. 27.

[0262] The first side and second side radiation members 503, 504 are,for example, made of Cu (copper). The bonding members 502 are made ofmaterial having high thermal conductivity, such as solder, or brazingfiller metal. Then, the surfaces 505 b of the Si chips 501 a, 501 b arefit in the recess portions 508 and bonded to the second side radiationmember 504 through the bonding members 502. The convex portions 506 ofthe first side radiation member 503 are bonded to the principalelectrodes of the surfaces 505 a of the Si chips 501 a, 501 b.

[0263] Further, the control electrode of the Si chips 501 a, 501 b iselectrically connected to the inner lead 510 of a lead frame 509 througha wire 511 by wire bonding. In FIG. 27, portions of the lead frame 509overlapping with other portions are indicated with dotted lines. Asdescribed later, the lead frame 509 has six fixation portions 509 a, 509b respectively having holes 512 a, 512 b for receiving the protrudingportions 507 a, 507 b of the first side and second side radiationmembers 503, 504. Here, Al (aluminum), Au (gold), or the like can beused for the wire 511, and Cu, Cu alloy, 42-alloy, or the like can beused for the lead frame 509.

[0264] Then, as shown in FIG. 28B, the protruding portions 507 b formedon the second side radiation member 504 are fit in the holes 512 bformed in the fixation portions 509 b of the lead frame 509, and arecaulked. On the other hand, each of the protruding portions 507 a formedon the first side radiation member 503 is fit in each of the holes 512 aformed in the fixation portion 509 a and caulked in a state where aspacer 513 is interposed between the first side radiation member 503 andthe lead frame 509.

[0265] The spacer 513 is a columnar or prismatic metal such as Cu, andhas a hole for allowing the protruding portion 507 a to penetrate it.The spacer 513 positions the first side radiation member 503 withrespect to the Si chips 501 a, 501 b in the thickness direction of theSi chips 501 a, 501 b. When the spacer 513 is a prism, for example, ithas a square cross-section with a side of 2 mm, and a thickness of about0.6 mm.

[0266] Further, as shown in FIGS. 27, 28A, and 28B, the Si chips 501 a,501 b, and the radiation members 503, 504 fixed as described above areso sealed with resin 514 that each surface of the first side and secondside radiation members 503, 504 at an opposite surfaces facing the Sichips 501 a, 501 b are exposed from the resin 514. In FIG. 27, thecontour of the resin 514 is indicated with a broken line. Of the stripportions 503 a, 503 b, 504 a, 504 b of the first side and second sideradiation members 503, 504, the strip portions 503 a, 504 b, whichextend in the direction opposite to the side where the inner lead 510 isconnected, protrude to the outside of the resin 514, and the externallyprotruding strip portions 503 a, 504 b respectively serve as outerelectrodes of the Si chips 501 a, 501 b.

[0267] Next, a method for manufacturing the semiconductor substrate isexplained. First, the lead frame 509, and the first side and second sideradiation members 503, 504, as shown in FIGS. 27, 28A, 28B are prepared.The lead frame 509 is formed into a desirable shape by, for example,punching.

[0268]FIGS. 30A to 30D schematically show a method for forming the firstside and second side radiation members 503, 504. As shown in FIG. 30A,the first side and second side radiation members 503, 504 are cut out ofa reel-shaped member 515 made of Cu or the like, the convex portions 506are formed on the first side radiation member 503, and the concaveportions 508 are formed on the second side radiation member 504, bypress working using a punch 516 and a die 517 while moving the punch 516in a direction indicated by an arrow F. FIGS. 30B to 30D show a processfor forming the protruding portions 507 a, 507 b. As shown in thefigures, extruding working is performed to form the protruding portions507 a, 507 b by using a punch 518 and a die 519 that has a recess at acenter thereof, and by moving the punch 518 in a direction indicated byarrows H.

[0269] Next, the Si chips 501 a, 501 b are assembled with the lead frame509 and the first side and second side radiation members 503, 504processed as described above. FIG. 31 schematically shows constitutionsof the respective members 501 a, 501 b, 502 to 504, and 509 viewed in aside face direction at this assembling step. As shown in FIG. 31, theprotruding portions 507 b of the second side radiation member 504 areinserted into the holes 512 b of the fixation portions 509 b of the leadframe 509, and are caulked. In the concave portions 508, the Si chips501 a, 501 b are fitly disposed at the side of the surface 505 b throughsolder foils 502 as bonding members.

[0270] Besides, solder foils 502 having shapes corresponding to those ofthe respective principal electrodes are disposed on the surfaces 505 aof the Si chips 501 a, 501 b. The spacers 513 are respectively attachedto the protruding portions 507 a of the first side radiation member 503.Then, the protruding portions 507 a are inserted into the holes 512 a ofthe fixation portions 509 a of the lead frame 509, and then caulked.Incidentally, the convex portions 506 of the first side radiation member503 are omitted in FIG. 7.

[0271] The caulking fixation at this assembling step is specificallyexplained below. FIGS. 32A to 32C schematically shows the step forcaulking fixation. As shown in FIGS. 32A and 32B, after the protrudingportions 507 a, 507 b of the first side and second side radiationmembers 503, 504 are fit in the holes 512 a, 512 b of the fixationportions 509 a, 509 b of the lead frame 509, the protruding portions 507a, 507 b protruding from the holes 512 a, 512 b are crushed by moving apunch 520 in a direction indicated by arrows I. Accordingly, as shown inFIG. 32C, the first side and second side radiation members 503, 504 andthe lead frame 509 are fixed to each other.

[0272] Successively, the Si chips 501 a, 501 b, the radiation members503, 504 and the lead frame 509 caulked together undergo solder reflowin a hydrogen furnace or the like, so that the members 501 a, 501 b,503, 504 are integrally fixed by soldering. After that, after wirebonding is performed between the control electrode on the surface 505 aof the IGBT chip 501 and the lead frame 509, sealing by the resin 514 isperformed by transfer mold. Accordingly, the insulation between thefirst side and second side radiation members 503, 504 are achieved, andthe semiconductor device in the present embodiment is completed.

[0273] According to the present embodiment, because the first side andsecond side radiation members 503, 504 are respectively bonded to theboth surfaces 505 a, 505 b of the Si chips 501 a, 501 b through thebonding member 502, the radiation property can be improved. Further, thebonding member 502 is made of adhesive material having high thermalconductivity such as solder or brazing filler metal. This furtherimproves the radiation property.

[0274] Besides, the Si chips 501 a, 501 b can be fixed to the secondside radiation member 504 by being installed in the recess portions 508of the second side radiation member 504. Further, and the first side andsecond side radiation members 503, 504 can be fixed with the lead frame509 by inserting the protruding portions 507 a, 507 b of the radiationmembers 503, 504 into the holes 512 a, 512 b of the fixation portions509 a, 509 b of the lead frame 509 and caulking them. As a result, therelative positions of these members can be fixed in a direction parallelto the surfaces of the Si chips 501 a, 501 b.

[0275] Also, the protruding portions 507 a of the first side radiationmember 503 are fit in the holes 512 a of the fixation portions 509 a ofthe lead frame 509 with the spacers 513 interposed between the firstside radiation member 503 and the lead frame 509. Because of this, thefirst side radiation member 503 can be fixed to the lead frame 509 whileproviding a mounting space for the Si chips 501 a, 501 b, and furthercan be positioned relatively in the thickness direction of the Si chips501 a, 501 b. Accordingly, the relative positions of the respectivemembers can be fixed in both the surface direction and the thicknessdirection of the Si chips 501 a, 501 b. The semiconductor device can beprovided with decreased variations in mounting positions of the members.

[0276] When a power element such as an IGBT is used as a semiconductorchip as in the present embodiment, there may arise the following problemregarding insulation. FIG. 33 shows an example of an IGBT.

[0277] As shown in FIG. 33, a power element such as an IGBT is formedwith a guard ring 521 and an EQR (equipotential ring) 522 at an edgeportion thereof, and the guard ring 521 and the EQR 522 are formed tohave approximately the same potential as that of a collector electrode523. The guard ring 521 and the EQR 522 are further formed on thesurface of the power element where an emitter electrode 524 is formed.That is, the guard ring 521 and the EQR 522 equipotential with thecollector electrode 523 exist in the vicinity of the emitter electrode524.

[0278] Therefore, in a case of the power element in which a potentialdifference between the emitter electrode 524 and the collector electrode523 is, for example, about 600 V, the potential difference between theguard ring 521, the EQR 522, and the emitter electrode 524 becomes alsoabout 600 V. Because of this, if a radiation member 525 is positionederroneously and shifted from an accurate position to the side of theguard ring 521 and the EQR 522 as shown in an arrow J in FIG. 33, theguard ring 521 and the EQR 522 might electrically communicate with theemitter electrode 524 through a bonding member 526 such as solder andthe radiation member 525 directly or by discharge. Even if the guardring 521 and the EQR 522 are covered with a protective film 527 made ofpolyimide or the like, the thickness of the film is about 1 to 2 μm atmost, and the withstand voltage to 600 V cannot be secured.

[0279] To the contrary, in the semiconductor device of the presentembodiment, as described above, in the state where the relativepositions of the Si chips 501 a, 501 b, the lead frame 509, and thefirst side and second side radiation members 503, 504 are fixed, theconvex portions 506 of the first side radiation member 503 are bonded tothe principal electrodes on the surfaces 505 a of the Si chips 501 a,501 b. Because of this, the first side radiation member 503 can bebrought in contact with only the principal electrodes by controlling theshape of the convex portions 506. This can also solve the problemconcerning the insulation, caused by the deviation of the relativeposition of the radiation member 503 from the Si chips 501 a, 501 b.

[0280] The present embodiment exemplifies the example in which thespacers 513 are fitly attached to the protruding portions 507 a of thefirst side radiation member 503; however, the protruding portions 507 a,507 b may be formed in a stepped shape on the respective radiationmembers 503, 504 by, for example, forming the die 519 used for extrudingprocessing shown in FIGS. 32B and 32C to have a stepped portion in therecess portion thereof. Thus, the spacers may be integrated with theprotruding portions.

[0281] Besides, the spacers 513 are not limited to be attached to theprotruding portions 507 a of the first side radiation member 503, butmay be attached to the protruding portion 507 b of the second sideradiation member 504 to fix the relative positions of the Si chips 501a, 501 b, the radiation members 503, 504, and the lead frame 509 in thethickness direction of the Si chips 501 a, 501 b.

[0282] As in the present embodiment, when both the first side and secondside radiation members 503, 504 are respectively fixed to the lead frame509 by caulking, the variations in mounting positions of thesemiconductor chips can be securely suppressed. However, only one of theradiation members 503, 504 may be fixed by caulking so long as thepositioning accuracy of the radiation members 503, 504 is improved andthe variations in mounting positions of the semiconductor chips aresuppressed.

[0283] Each of the radiation members 503, 504 has a surface externallyexposed at an opposite side of the Si chips 501 a, 501 b. The exposedsurface may be brought in contact with a cooling member for acceleratingthe radiation of heat. The present embodiment exemplified the IGBT chip501 a as a semiconductor chip, and is so constructed that the variationsin mounting position of the semiconductor chip is suppressed. Even whenthe radiation members 503, 504 are not used as electrodes, theconstitution of the present invention is effective to improve theradiation property and to prevent the variations in mounting position ofthe semiconductor chip.

[0284] The spacers 513 are attached to all (three in the presentembodiment) of the protruding portions 507 a formed on the first sideradiation member 503; however, the spacers provided at two locations aresufficient to fix the relative positions between the first sideradiation member 503 and the Si chips 501 a, 501 b in the thicknessdirection of the Si chips 501 a, 501 b. The bonding members 502 are notlimited to the solder foils, but may be solder paste or the like. Thesemiconductor device needs not always have the two semiconductor chips501 a, 501 b, and have only to have one chip.

Eighteenth Embodiment

[0285] When the current capacity of the IGBT chip 501 a exceeds 100A,the chip size is increased, and there is a case the chip size becomes 10to 16 mm. When the radiation members 503, 504 are made of Cu in such acase, since the linear expansion coefficient of Cu is 5 to 6 timeslarger than that of Si constituting the IGBT chip 501 a, solderconstituting the bonding member 502 is thermally fatigued in a thermalcycle. This may results in occurrence of cracks, increase in thermalresistance, and deterioration in the heat radiation property.

[0286] In this connection, an eighteenth preferred embodiment of thepresent invention has been made as follows. In this embodiment, thefirst side and second side radiation members 503, 504 are made ofmaterial different from that of the first embodiment. Hereinafter,different portions from those in the seventeenth embodiment are mainlydescribed, and the same parts as those in the seventeenth embodiment areassigned to the same reference numerals.

[0287] As shown in FIG. 34, as the first side and second side radiationmembers 503, 504, metal having a leaner expansion coefficient similar tothat of Si chips 501 a, 501 b is used. Specifically, as an example, cladmembers (CICs) each of which is so constructed that a member (invarmember) 528 made of invar is sandwiched by members (Cu members) 529 madeof Cu are adopted. The linear expansion coefficient of each CIC isapproached to that of Si as close as possible by controlling the ratioin thickness between the invar member 528 and the Cu members 529, andthe total thickness. The other members and features such as shapes aresubstantially the same as those in the seventeenth embodiment.

[0288] According to the eighteenth embodiment, because the linearexpansion coefficient of the first side and second side radiationmembers 503, 504 is approximated to that of the Si chips 501 a, 501 b,even when each size of the chips 501 a, 501 b is large, thermal stressthat is caused by the difference in thermal expansion coefficientbetween the Si chips 501 a, 501 b and the radiation members 503, 504 canbe suppressed, and concentration of strain on the bonding members 502can also be prevented. This prevents the deterioration in bondingproperty between the radiation members 503, 504 and the Si chips 501 a,501 b. In consequence, the deterioration in radiation property and thedecrease in electrical conductivity when the radiation members 503, 504are used as electrodes can also be prevented.

[0289] The same effects as described above can be exhibited when Mo(molybdenum) is used in place of invar. In the radiation members 503,504, the members 528 sandwiched by the Cu members 529 need not beunified to the invar or Mo member, and may be different from each other.The radiation members 503, 504 are not limited to the clad members, butmay be other members such as Cu—Mo alloy having a linear expansioncoefficient approximated to that of Si.

[0290] Incidentally, the eighteenth embodiment indicates an exampleusing metal having a linear expansion coefficient approximated to thatof Si, for the radiation members 503, 504, and adopts the clad memberssuch as CIC as an example. However, thermal conductivities of invar andMo are inferior to that of Cu, and the invar or Mo members 528 lower theradiation property in the thickness direction of the Si chips 501 a, 501b. The following modified embodiment solves this problem.

[0291] In this modified embodiment, as shown in FIGS. 35A and 35B,several invar members 528 are partially layered in the Cu member 529.FIG. 35A shows a cross-sectional view showing the radiation member 503,504 cut in a direction parallel to the layer where it includes the invarmembers 528, while FIG. 35B shows a cross-sectional view showing theradiation member 503, 504, cut in a direction perpendicular to the layerwhere it includes the invar members 528.

[0292] As shown in FIGS. 35A and 35B, in this modified embodiment, theinvar members 528 are provided at several (four) positions inside the Cumember 529. Accordingly, the radiation member 503, 504 has portions thatare composed of only the Cu member 529 in the thickness directionthereof, so that the thermal conductivity in the thickness direction ofthe radiation member 503, 504 are not lessened. Thus, the radiationmember approximated to Si in thermal expansion coefficient can beprovided with sufficient radiation property. In this modifiedembodiment, although the invar members 528 are provided at fourpositions inside the Cu member 529, the invar members 528 may be formedinto a fine mesh by, for example, providing many small sized invarparts. Mo members can be used in place of the invar members. Otherwise,the invar members and the Mo members are used simultaneously.

[0293]FIG. 36 shows a semiconductor device as another modifiedembodiment. In the seventeenth and eighteenth embodiment describedabove, the control electrode on the surface 505 a of the IGBT chip 501 ais electrically connected to the inner lead 510 by wire bonding;however, as shown in FIG. 36, the connection may be made by abump-shaped bonding member 530 made of solder or the like. Accordingly,when soldering is performed between the first side and second sideradiation members 503, 504 and the Si chips 501 a, 501 b, the connectionbetween the inner lead 510 and the control electrode can be formedsimultaneously. This results in simplification of the manufacturingprocess.

[0294] While the present invention has been shown and described withreference to the foregoing preferred embodiments, it will be apparent tothose skilled in the art that changes in form and detail may be madetherein without departing from the scope of the invention as defined inthe appended claims.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor chip: first and second radiation members thermally andelectrically connected to the semiconductor chip interposedtherebetween, and having a radiation surface for radiation heat from thesemiconductor chip; and first and second bonding members respectivelyinterposed between the first radiation member and the semiconductor chipand between the semiconductor chip and the second radiation member,wherein: the first and second radiation members are made of a metallicmaterial that is superior to tungsten and molybdenum in at least one ofan electrical conductivity and a thermal conductivity.
 2. The methodaccording to claim 1, further comprising an insulating film provided ona surface of one of the first and second radiation members at a side ofthe semiconductor chip, at a region other than a region where the one ofthe first and second radiation members are bonded to the semiconductorchip through one of the first and second bonding members.
 3. The methodaccording to claim 2, wherein: the semiconductor chip has a guard ringat an edge portion thereof, the guard ring facing the insulating filmprovided on the one of the first and second radiation members; and theinsulating film has an opening facing an inner portion of thesemiconductor chip than the edge portion where the guard ring isprovided.
 4. The semiconductor device according to claim 1, wherein theradiation surface is composed of first and second radiation surfacesthat are respectively side faces of the first and second radiationmembers, and are coplanar with each other.
 5. The semiconductor deviceaccording to claim 1, further comprising a conductive member protrudingfrom a surface of one of the first and second radiation members otherthan the radiation surface, for electrically connecting thesemiconductor chip to an outside.
 6. The semiconductor device accordingto claim 5, wherein the conductive member has first and secondconductive members respectively protruding from first and secondpositions of the first and second radiation members in parallel witheach other, the first and second positions being approximately identicalwith each other in a direction perpendicular to the radiation surface.7. The semiconductor device according to claim 1, wherein the first andsecond radiation members respectively have first and second radiationsurfaces each of which is provided at an opposite side of thesemiconductor chip, and exposed to an outside for radiating heat.
 8. Thesemiconductor device according to claim 7, further comprising an outsidewiring member disposed on the first radiation surface, wherein: thefirst radiation member has a screw hole opened on the first radiationsurface and having a closed bottom; the outside wiring member has athrough hole at a position corresponding to the screw hole; and a screwis inserted into the through hole and the screw hole to fix the outsidewiring member to the first radiation member.
 9. The semiconductor deviceaccording to claim 1, wherein each of the first and second radiationmembers has a space at an inside thereof for reducing rigidity thereof.10. The semiconductor device according to claim 1, wherein the metallicmaterial contains one of copper and aluminum as a main component. 11.The semiconductor device according to claim 1, wherein the semiconductorchip and the first and second radiation members are sealed with a resinhaving a thermal expansion coefficient approximate to that of the firstand second radiation members.
 12. The semiconductor device according toclaim 1, wherein: each of the first and second bonding members iscomposed of a plurality of bumps that form a plurality of spacestherebetween; and the plurality of spaces provided among the pluralityof bumps are filled with a resin.
 13. The semiconductor device accordingto claim 1, wherein each of the first and second radiation members has ametallic portion at least as a part of a portion thereof facing thesemiconductor chip, the metallic portion having a thermal expansioncoefficient approximate to that of the semiconductor chip.
 14. Asemiconductor device, comprising: first and second semiconductor chips:and first and second radiation members thermally and electricallyconnected to the first and second semiconductor chips interposedtherebetween through a bonding member, and having a radiation surfacefor radiation heat from the first and second semiconductor chips,wherein: the first radiation member has first and second protrudingportions protruding toward the first and second semiconductor chips; andfirst and second front end portions of the first and second protrudingportions are thermally and electrically connected to the first andsecond semiconductor chips through the bonding member.
 15. Thesemiconductor device according to claim 14, wherein the radiationsurface is composed of first and second radiation surfaces of the firstand second radiation members, the first and second radiation surfacesbeing respectively provided at an opposite side of the first and secondsemiconductor chips and being approximately parallel to each other. 16.The semiconductor device according to claim 14, wherein the radiationsurface is composed of first and second radiation surfaces that are sidefaces of the first and second radiation members, and are approximatelycoplanar with each other.
 17. The semiconductor device according toclaim 14, further comprising an insulating film provided on one of thefirst and second radiation members at a side facing the first and secondsemiconductor chips, and at a portion other than portions connected tothe first and second semiconductor chips through the bonding member. 18.The semiconductor device according to claim 14, further comprising aconductive member protruding from one of the first and second radiationmembers other than the radiation surface, for electrically connecting atleast one of the first and second semiconductor chips to an outside. 19.The semiconductor device according to claim 18, wherein the conductivemember has first and second conductive members respectively protrudingfrom first and second positions of the first and second radiationmembers in parallel with each other, the first and second positionsbeing approximately identical with each other in a directionperpendicular to the radiation surface.
 20. The semiconductor deviceaccording to claim 14, further comprising an outside wiring memberdisposed on the radiation surface that is provided on a surface of oneof the first and second radiation members at an opposite side of thefirst and second semiconductor chips, wherein: the one of the first andsecond radiation members has a screw hole opened on the radiationsurface and having a closed bottom; the outside wiring member has athrough hole at a position corresponding to the screw hole; and a screwis inserted into the through hole and the screw hole to fix the outsidewiring member to the one of the first and second radiation members. 21.The semiconductor device according to claim 14, wherein each of thefirst and second radiation members has a space at an inside thereof forreducing rigidity thereof.
 22. The semiconductor device according toclaim 14, wherein at least one of the first and second radiation membersis made of a metallic material containing one of copper and aluminum asa main component.
 23. The semiconductor device according to claim 14,wherein the first and second semiconductor chips and the first andsecond radiation members are sealed with a resin having a thermalexpansion coefficient approximate to that of the first and secondradiation members.
 24. The semiconductor device according to claim 14,wherein: the bonding member is composed of a plurality of bumps thatform a plurality of spaces therebetween; and the plurality of spacesprovided among the plurality of bumps are filled with a resin.
 25. Asemiconductor device, comprising: a semiconductor chip having an elementformation surface and a back surface: a first conductive member bondedto the element formation surface of the semiconductor chip through afirst bonding member having electrical conductivity; a second conductivemember bonded to the back surface of the semiconductor chip through asecond bonding member having electrical conductivity; and a thirdconductive member bonded to the first conductive member through a thirdbonding member having electrical conductivity, at an opposite side ofthe semiconductor chip, wherein a bonding area between the firstconductive member and the third conductive member is smaller than thatbetween the first conductive member and the semiconductor chip.
 26. Thesemiconductor chip according to claim 25, wherein the semiconductorchip, the first, second, and third conductive members are sealed with asealing member to expose at least a surface part of one of the secondand third conductive members from the sealing member.
 27. Thesemiconductor device according to claim 26, wherein the first conductivemember has a step portion facing an outer periphery of the resin, thestep portion forming a thin thickness portion of the first conductivemember.
 28. The semiconductor device according to claim 27, wherein thestep portion of the first conductive member is covered with the sealingmember.
 29. The semiconductor device according to claim 27, wherein thefirst conducive member partially protrudes toward the third conductivemember with the thin thickness portion facing the semiconductor chip.30. The semiconductor device according to claim 26, wherein an outersurface portion of the first conductive member contacting the sealingmember is oxidized.
 31. The semiconductor device according to claim 25,further comprising an electrode provided on the element formationsurface of the semiconductor chip, wherein: an area of the electrode isapproximately equal to the bonding area between the first conductivemember and the semiconductor chip.
 32. A semiconductor device,comprising: a semiconductor chip having an element formation surface anda back surface at an opposite side of the element formation surface; afirst conductive member electrically connected to the element formationsurface of the semiconductor chip; a second conductive memberelectrically connected to the back surface of the semiconductor; a thirdconductive member electrically connected to the first conductive memberat an opposite side of the semiconductor chip; and a sealing membersealing the element formation surface and the back surface of thesemiconductor chip respectively electrically connected to the first andsecond conductive members, and a face of the third conductive memberelectrically connected to the first conductive member, wherein: thefirst conductive member has a step portion at a portion facing an outerperiphery of the sealing member, the first conductive member having athin thickness portion by providing the step portion.
 33. Thesemiconductor device according to claim 32, wherein the step portion ofthe first conductive member is covered with the sealing member.
 34. Thesemiconductor device according to claim 32, wherein the first conducivemember partially protrudes toward the third conductive member with thethin thickness portion facing the semiconductor chip.
 35. Thesemiconductor device according to claim 32, wherein an outer surfaceportion of the first conductive member contacting the sealing member isoxidized.
 36. The semiconductor device according to claim 32, furthercomprising an electrode provided on the element formation surface of thesemiconductor chip, wherein: an area of the electrode is approximatelyequal to a bonding area between the first conductive member and thesemiconductor chip.
 37. A semiconductor device, comprising: a substratemade of Si, having an element formation surface and a back surface at anopposite side of the element formation surface; an electrode formed onthe element formation surface of the substrate and made of pure Alexcluding an impurity; and a barrier metal disposed between theelectrode and the substrate, for preventing Si from being dissolved inthe electrode.
 38. The semiconductor device according to claim 37,further comprising a back side electrode formed on the back surface ofthe substrate and made of pure Al excluding an impurity;
 39. Thesemiconductor device according to claim 37, further comprising a firstradiation member bonded to the main surface of the substrate through theelectrode to radiate heat generated from a semiconductor chip composedof the substrate and the electrode.
 40. The semiconductor deviceaccording to claim 39, wherein a direction in which the heat is radiatedby the first radiation member corresponds to a direction progressingfrom the element formation surface to the back surface of the substrate.41. The semiconductor device according to claim 39, further comprising:a second radiation member bonded to the back surface of the substrate,and having a radiation surface; and an outside cooling member contactingthe radiation surface of the second radiation member at an opposite sideof the substrate for facilitating radiation of the heat to an outside,wherein; the first radiation member is connected to the second radiationmember so that the heat generated from the element formation surface isradiated from the radiation surface of the second radiation member. 42.The semiconductor device according to claim 41, further comprising ahigh thermal conductivity substrate having high thermal conductivity anddisposed between the first radiation member and the second radiationmember.
 43. A semiconductor device, comprising: a semiconductor chiphaving a first surface and a second surface: a first radiation memberbonded to the first surface of the semiconductor chip through a firstbonding member having thermal conductivity; and a second radiationmember bonded to the second surface of the semiconductor chip through asecond bonding member having thermal conductivity, the second radiationmember having a concave portion for holding therein the semiconductorchip therein.
 44. The semiconductor device according to claim 43,wherein: the first radiation member has a convex portion protrudingtoward the semiconductor chip; and the convex portion is bonded to thesemiconductor chip through the first bonding member.
 45. Thesemiconductor device according to claim 43, further comprising: acontrol electrode provided on the first surface of the semiconductorchip; and a lead frame electrically connected to the control electrode.46. The semiconductor device according to claim 45, wherein one of thefirst radiation member and the second radiation member has a protrudingportion at a side of the semiconductor chip, the protruding portionbeing inserted into a hole formed in the lead frame to fix the one ofthe first radiation member and the second radiation member to the leadframe.
 47. The semiconductor device according to claim 45, wherein oneof the first radiation member and the second radiation member has aprotruding portion at a side of the semiconductor chip, the protrudingportion being inserted into a hole formed in the lead frame with aspacer interposed between the lead frame and the one of the firstradiation member and the second radiation member, the spacer positioningthe one of the first radiation member and the second radiation memberwith respect to the semiconductor chip in a thickness direction of thesemiconductor chip.
 48. The semiconductor device according to claim 43,wherein one of the first radiation member and the second radiationmember is composed of a copper member and a plurality of portionsdisposed partially inside the copper member and made of one of invar andmolybdenum.
 49. The semiconductor device according to claim 43, whereinthe first radiation member, the semiconductor chip, and the secondradiation member are sealed with a resin member in a state where each ofthe first radiation member and the second radiation member has a surfaceexposed from the resin member at an opposite side of the semiconductorchip.
 50. A semiconductor device, comprising: a semiconductor chiphaving a first surface and a second surface: a first radiation memberhaving a convex portion that is bonded to the first surface of thesemiconductor chip through a first bonding member having thermalconductivity; and a second radiation member bonded to the second surfaceof the semiconductor chip through a second bonding member having thermalconductivity; a control electrode provided on the first surface of thesemiconductor chip; a lead frame electrically connected to the controlelectrode, wherein: one of the first radiation member and the secondradiation member has a protruding portion at a side facing thesemiconductor chip; the protruding portion is fixedly inserted into ahole formed in the lead frame to fix the one of the first radiationmember and the second radiation member; and a spacer is disposed in aspace defined between the one of the first radiation member and thesecond radiation member to position the one of the first radiationmember and the second radiation member, and the semiconductor chip in athickness direction of the semiconductor chip.
 51. The semiconductordevice according to claim 50, wherein the first radiation member and thesecond radiation member are made of a metallic material having a linearthermal expansion coefficient approximate to that of the semiconductorchip.
 52. The semiconductor device according to claim 50, wherein one ofthe first radiation member and the second radiation member is composedof a copper member and a plurality of portions disposed partially insidethe copper member and made of one of invar and molybdenum.
 53. Thesemiconductor device according to claim 50, wherein the first radiationmember, the semiconductor chip, and the second radiation member aresealed with a resin member in a state where each of the first radiationmember and the second radiation member has a surface exposed from theresin member at an opposite side of the semiconductor chip.
 54. Asemiconductor device, comprising: a semiconductor chip having a firstsurface and a second surface; a first conductive member bonded to thefirst surface of the semiconductor chip through a first solderingmember; and a second conductive member bonded to the second surface ofthe semiconductor chip through a second soldering member, a fusing pointof which is lower than that of the first soldering member.
 55. Thesemiconductor device according to claim 54, wherein the second solderingmember contains Sn at 90 wt % at least.
 56. The semiconductor deviceaccording to claim 54, wherein the second conductive member has a recessportion in which the second soldering member is disposed.
 57. Thesemiconductor device according to claim 54, wherein each of the firstradiation member and the second radiation member serves simultaneouslyas an electrode and a radiation member for the semiconductor chip.
 58. Amethod for manufacturing a semiconductor device, comprising: bonding asemiconductor chip to a first conductive member with a first solderingmember interposed therebetween; bonding a second conductive member tothe semiconductor chip with a second soldering member interposedtherebetween, the second soldering member having a fusing point lowerthan that of the first soldering member; performing a reflow treatmentonly to the second soldering member; and applying a pressure to thesecond conductive member from a side opposite to the semiconductor chipto control a degree of parallelization between the first conductivemember and the second conductive member.
 59. The method according toclaim 58, wherein the second conductive member contains Sn at 90 wt % ormore.
 60. A method for manufacturing an electronic instrument,comprising: interposing a heating element between first and secondradiation members-through a bonding member; interposing a jig in a spacedefined between the first and second radiation members so that the jigcontacts the first and second radiation members, the jig being forfixing a distance between the first and second radiation members;externally pressurizing the first and second radiation members to bondthe first and second radiation members and the heating element with thebonding member.
 61. The method according to claim 60, wherein the jighas a thermal expansion coefficient larger than those of the first andsecond radiation members.
 62. A method for manufacturing an electronicinstrument, comprising: interposing a heating element between firstsurfaces of first and second radiation members with a first bondingmember interposed between the first surface of the first radiationmember and the heating element, and a second bonding member interposedbetween the first surface of the second radiation member and the heatingelement; preparing a first jig having a first protruding portion on afirst jig surface thereon, and a second jig having a second protrudingportion on a second jig surface thereon; disposing the first jig withthe first jig surface facing a second surface of the second radiationmember, and the second jig with the second jig surface facing a secondsurface of the first radiation member; making a front end portion of thefirst protruding portion abut the first surface of the first radiationmember, and making a front end portion of the second protruding portionabut the first surface of the second radiation member while keeping adistance between the first jig and the second jig constant; andpressuring the first and second radiation members from the secondsurfaces of the first and second radiation members to bond the first andsecond radiation members and the heating element with the first andsecond bonding members.
 63. The method according to claim 62, whereinthe first radiation member has a through hole through which the secondprotruding portion passes.
 64. The method according to claim 63, whereinthe second radiation member has a through hole through which the firstprotruding portion passes.
 65. The method according to claim 62, whereinthe first and second radiation members are pressurized by an elasticforce of a spring member.